Because the global shift in football playing style has been towards the functional and the athletic, meaning all leagues have dipped. By definition, the league that has been the closest to that in style would do better. As they have bigger finances due to insane commercial deals, the PL sides can also spend more in acquiring these functional athletes.
It is the natural culmination of team focused systems and data analysis in football (and I'm not against data in football, I think it's useful and we should use it more). It means that teams want to develop systems players as opposed to mavericks etc. Even Brazilian academies changed their focus years ago, because they knew they would make more money producing functional athletes for European leagues than another Ronaldinho.
Even Guardiola's Barca team was obsessed with the system, it just had unbelievable players in it too and all styles now lead to the functional aspect of football. If you also factor in the money in the PL, the owners have even more of an incentive to remain, so again emphasise competitive athleticism over all else. Again, nothing wrong with that, but it means that we have reached a cyclical event where play styles have trended back towards the styles of the 80s and 90s, just with modern formations and a much higher level of athleticism.
Maybe it will change again in a few years. But the standard is objectively terrible in all the major leagues now.