They already mentioned planning or writing for it a while ago IIRC, it's very Netflix to think far ahead and prepare to make more seasons and such.
The new (terrible) Wednesday show ended on a massive, gamechanging cliffhanger and opened a LOT of doors so to speak, so it was unsurprising when it got confirmed to get another season, even before all the disingenuously and undeservedly rave reviews and reception it got.
https://www.sportskeeda.com/anime/n...leak-suggests-writing-season-2-to-be-underway
I swear I remember seeing Matt saying a season 2 was in planning or even preproduction.