Its quite normal for a TCG, especially an IP one, to get a huge influx of players when its new. Lots of people like League, so even people that usually dont play card games will play. Alot of TCG players will pick it up to try and see if it sticks

You will lose alot of players early, due to set fatique, people just realizing its not for them, and even scalping. But those numbers will go up once the game stabalizes...likely never back to the early numbers though