It's a few things I think:

Long Island kids start playing very early and together. PA has kids that start young, but not to numbers that kids in LI do.

They have lots of money. Not that PA doesn't, but it doesn't compare.

I saw an interview with the guy who coaches team 91. He coaches the lizards and also the stony Brooke women's team. He talked about how because of his MLL ties, his kids get a chance to play around with some of these MLL players, see their work ethic, how they practice and prepare and learn advanced stuff early on. He coached their 2020 team that dominated everyone out in Denver.