#1 The Owners' will
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There are other rich owners, like Arsenal's Stan Kroenke for instance, who has stated on record that, “If you want to win championships then you would never get involved.” In fact, Manchester United, one of the world's richest clubs, do not sanction deals that they feel might be over their valuation.
However, the same hasn't been the case with Manchester City and over the years, as they have hardly ever had to let go of one of their targets due to a refusal to meet the financial demands of the selling club. That boils down to the immense wealth of the club's owners and their willingness to back the club completely when it comes to player acquisitions.
Other clubs will obviously judge whether a club backed by the immense riches of a nation state is ethical or not, but the reality remains that Manchester City's riches will almost always see them competing for the best players and get their way more often than not, through the sheer power of their seemingly bottomless pockets.
In addition to that, one can expect that spending will eventually be scaled back a lot once the club's finances and revenues are on an equal footing with the rest of the footballing elite. A self-sustaining future might be on the horizon a decade into the future and once that happens, the other factors cited here will make Manchester City a club that will be unmatched in England. Their period of dominance may just have begun already.