Premier league has a great success because they are viewed in a lot more nations, and they get a lot more money involved as well. I do not know where all this billions of dollars come from aside from selling your club to some rich person, but they do have a lot of money. When you have a lot of money that means your income is good and when your income is good then you can pay for high salaries and when you can pay for high salaries then you can get any player you want.
Look at United, they had zero interest on Ronaldo when the season started because they believed he wasn't available, he would be in Juventus but the moment he got available they just paid whatever and then gave him whatever salary and moved on, they had literally extra money aside to make that move, 99.99% of the teams on the world wouldn't even have been able to do that financially let alone convince Ronaldo to come.
Currently, English Premier League is world's most soccer league and just because of this they have good income from media right and after this there are some good investors now involved in which are putting Billions of USD for their own sack just because of this they have some good income, but one thing is sure Europe's top 5 leagues have not big difference because I was checking few statics it is showing England, Italy, Germany.
Spain and France are currently top ranked, but England is going with good advantage mostly just because of English way but Barcelona, Real Madrid and Bayern Munch are also not bad at all they have some good income as well.