So personal anecdotes about that -
I grew up playing soccer (and still do at 35) and have always enjoyed watching it, but have typically watched american football as well. In the last few years, as it's been easier to catch international soccer *and* MLS on TV I've definitely been watching more soccer than american football. I live in New England so it's not like I don't have a good team to watch either. Anyways one of the natural drivers of that has just been flow of play - american football is best watched on a DVR with a 30s skip button, and just bogs down endlessly (the irony being is that I'll put baseball on TV regularly, but more as background entertainment). Soccer you know will only last so long and aside from random injuries/fake injuries never stops. So growing up with soccer, all that about play, TV coverage expanding, going live actually being fun, and the CTE thing (sadly Soccer does have a CTE issue as well, just tiny in comparison) has shifted my attentions.
Annnnyways again, point of all that is that for me the shift isn't surprising. What is surprising is my brother in law - he grew up in and still lives in NYC and is/was a hardcore Yankees/Giants fan. Never played or watched soccer growing up. Before he had kids he'd watch almost every Yankees game, and still watches almost every Giants game. As NYC gained the Red Bulls, and later NYCFC, he started sorta migrating over and would start watching Premier League too. The kids he teaches are far more interested in Soccer than other sports. Nowadays he follows NYCFC pretty closely (he sorta grew to hate the Red Bulls), only occasionally watches baseball, and still follows the Giants but nothing like he used to.
So while we are on the opposite ends of where you'd start to get into soccer as an american, we both sorta migrated over to following it more than other sports for similar reasons. It definitely feels like between international league coverage on US TV and MLS' very steady growth and refinement soccer is really on the upward path now here. I thought maybe Lacrosse would take focus as american football started falling off, but it seems like people are shifting over to soccer instead.