I don't know if you're being obtuse or are genuinely posting this stuff in an honest to goodness way...
First and foremost it is highly debateable whether the star players who came through City's doors during that time were being paid only the documented book value. This, in itself is huge. If one states they have purchased a player for, say, £70m and are paying said player, say, £350,000 a week, when in reality, the cost was double and the weekly wage triple, that is an enormous disparity and advantage over anyone else. There is serious doubt over the cost of Haaland as but one example of many. If the documented value is incongruent with his actual cost, that is a player, instrumental to their treble who no other club could have obtained at face value. Multiply these allegations by a magnitude of order, and you already have a chasm between City and any so-called rival.
Secondly, if you are being held accountable, you spend money in a way that is essentially dictated to you (as agreed upon by all clubs in the league), with limit and restrictions in situ, which means you hit your financial limit for a period and can no longer make additional purchases that could be the icing on the cake for a particular window/season. If you are fiddling the books, you can stretch these parameters by as much as can be gotten away with before it is clearly an absurdity. City cycled through and fine tuned their squad under great suspicion. It isn't just a case of spending; it's being able to stretch and make something more malleable than anyone else can - when your £1 is everyone else's £5, you're going to have a massive advantage over the competition.
Thirdly, if you have bolstered a squad via illegal means, it is highly likely said squad will have obvious advantages over others, especially in terms of strength/depth, rotation and recovery. This is where insane points totals can be normalised with a squad that is "magically" fresher than everyone else's and a deeper pool of quality (see 1st and 2nd paragraphs) individuals to pick from and utilise.
Financial doping gives a team avenues to win that are not available to others. What you will normally find is that even if a rival team can keep up for a season or two, the consequence will be that that group of players will end up absolutely spent, exhausted, which is why City had no direct competitor who could run alongside them for 4 years straight, instead achieving 2 top level seasons with recovery ones dotted along the tapestry. If all teams were playing on an even footing, their bolstered squads would be able to rest and recover as readily as City's and keep up with them with simple strength in depth.
Magical things happening via magical means isn't magic at all, is it?