Very few football clubs run at a profit, whether challenging for promotion or scrambling for safety.
Ambitious clubs in the Championship are competing for the chance to get into the Premier League, however unless they are already well established and have a decent squad (ie recently relegated from the Prem) they will need to buy in quality.
Quality players in the Championship are now being 'routinely' sold for £10-20m, or even more. Such players do not typically stay with clubs at which they are not surrounded by quality and they do not typically move from one Championship team to another - a Championship team bidding on a real quality player from another Championship team will alert Premier League teams who will think "He's potentially Premier League quality... £10-15m? Not a problem". Because of the Premier League hoovering up real quality players a club attempting to improve their lot must first keep hold of their quality (not easy unless they're on good wages) and supplement it with more quality, however they're generally shopping only for players deemed not good enough for the Premier League, even though that's where they hope to be in 12 months time. In other words they're likely shopping for players who will offer only marginal gains, rather than game changers, unless of course they are lucky enough to stumble across a player who the Premier League teams with their army of scouts aren't aware of (or incorrectly don't rate).
So, generally speaking championship clubs are buying in players who offer marginal gains and paying maybe £3-5m for those marginal gains. EFL rules will work for clubs with a good foundation, a solid squad needing nothing more than a tweak.
Allow me to tell a story...
Amongst the melee of Championship sides exists a club which has been in the doldrums for a while, circling the drain in the Championship and occasionally yoyo-ing between that and League One for the best part of two decades... they get taken over by a 'rich' owner. They arguably have a squad of overachieving players - they've just finished midtable with a team of cast-offs, has beens and never have beens who would be more suited to a relegation dogfight than a promotion push, barring one or two bright sparks... it's been a 'great' season but 'greatness' has just been redefined, the crosshairs have now been set on promotion, the fans expect and theclub know they need to invest in the playing side if they want to do better.
Theres a feelgood factor around the club, the giant can be awoken and returned to former glories, all it needs is eight or nine quality first team players and another six or seven who can push them for places... so just 16 or so quality players, each costing £3-5m (unless they can polish a few turds along the way)... or they could shop in the Premier League bargain bin for released players on the decline; even then they'll have to offer seriously good wages for players who are reaching the twilight of their careers and have little to no resale value.
They get off to a good start in their first full season of new ownership by going down the free transfer / high wages route and riding the wave of excitement, anticipation and general good feeling around the club but they fall just short, losing in the play-off final. They've already taken their budget into the FFP dangerzone (they cant really afford another season of similar budget stretching) but now they theoretically only need two or three real quality players, the missing pieces in the jigsaw. So they go big, turfing out some larger transfer fees and bringing in a headline veteran striker who redefines the wage structure at the club. Existing players get wind of this and realised they're now underpaid relative to their worth and to certain colleagues, one player even refuses to play a game. Eventually calmness is returned at the expense of an extra million or three added to the annual cost of wages. They 'fail' that season, finishing fourth (higher than they actually did the season before) and losing on penalties in the play-offs. The fans deem the season to be a disaster.
More marginal gains are required but they've reached a crossroads... the squad is another year older and marginal gains are more difficult to identify, they can't afford to actually spend any money as the leap from relegation fodder to challengers has well and truly burst the FFP barriers... they're going to have to go into a slightly more 'experimental' phase, eeking out the final few drops of quality from existing players whilst picking up unknown players from the Dutch / German leagues and adding in occasional loans which may or may not work... unless they change track and go for a more sustain, slower build... but theres nothing 'sexy' about having tonnes of money to spend and not spending it... The club poll their fans on the ongoing strategy and the fans speak loudly on continuation of existing strategy of retaining quality and adding to it, rather than selling to buy.
This strategy doesn't work and a string of managers come and go as they try to get the winning formula. All the while they still need to trim the wage budget... they need to sell their decent players but who to? Who will take them on decent wages and with the downward trajectory of their careers reaching its steepest section? They'll just have to let contracts run down...
All the while new Managers want new players and theres EFL trouble on the horizon, they're under an embargo but gain EFL consent to 'sell the ground' to loosen the FFP noose around their neck... only it turns out they shouldn't have done that and now they're under threat of a points deduction, a season which was promising so much goes well and truly off the rails and they're lucky to avoid relegation with the post Christmas form being absolutely horrendous.
Morale of the story - 'Rich' owners breed expectations but 'rich' owners cannot really meet those expectations unless they have a naturally advantageous platform in terms of playing staff to start with in an environment where they can only buy half a team of top end Championship players (not good enough for the Prem) due to an arbitrary cap on losses. There's bugger all to gain from having a 'rich' owner if the club is starting low and has a strategy to slowly build over ten years, complying with FFP. A destitute owner can arguably do that. So what benefit a rich owner at a traditionally 'big' club in a world with spending caps? With the odd exception, the rules keep the small clubs small, the sleeping giants sleeping and the Premier League yoyo clubs yoyoing.