There are a few factors that I think make this year a standout for quantity of great games released:

1. Tons of games that were delayed due to the pandemic released this year, giving us several years' worth of ideas and work all at once.
2. The games industry saw massive layoffs this year--that's a ton of talent cut loose that now isn't going towards future games, and another step towards the inevitable reckoning over the abusive labor environment that games are made in. Whether that's a collapse or labor organization and the establishment of a long-overdue union, it's going to create a churn period that isn't going to produce a lot of games.
3. The glut of great games has saturated the market, meaning that games are returning less per investment dollar. This makes investors less eager to put their money towards new games, which leads to fewer games being made.