Marketshare of EA services is insane. They only have a very limited amount of games to offer, the monthly fee is much lower (except for premier) and yet they generate a large amount of revenue.
GamePass will only grow with further additions of new games at launch. (just imagine Gears 5 or Halo Infinite). Also the PC release even though I think that it won't have that much impact. Unless they turn it into a streaming service on PC.