I don't think it had anything to do with finance, the EPL has always had financial dominance over the other leagues.
What we're seeing now is the dual impact of the EPL signing the best managers from other leagues, and the top teams from outside of England going through a transition period (Real and Barca). A similar thing happened in the mid 2000's. Real's galaticos era was finishing with their best players entering their 30's while Barcelona's superstars lost motivation after 2006. A few years later, both were able to rebuild their squads and hire great managers (Jose and Pep) while the EPL squads that dominated went past their prime, Chelsea also lost Jose and Liverpool lost Rafa for example.
Liverpool's squad will too enter a period in a few years where some of their main players will go past 30 (Salah, Mane, Firmino, VvD) and Klopp might leave, that could signal a end to their dominance. City and Chelsea's squad look better in that respect but that depends on whether they can keep their current managers as well.
Let's see if Madrid and Barca can rebuild their squads in those next few years as well.