The Avengers made it that way when they removed the power stone from the timestream. The Ancient One explicitly says that removing a stone like that causes time to split. Thanos and his army came from the splinter timeline which never led to any of the movies anyway. And when the stone was returned, it prevented that timeline from existing at all which means Thanos et al came from a non-existant timeline and there is literally no one anywhere who will ever miss them.
Except Nebula still being around with all her memories from that timeline. And I don't recall Gamora turning to dust, though she wasn't there at the end unless there's something I missed, the Galaxy crew thinks she's out there somewhere.