Engagement helps algorithms determine what content to push to users, and misinformation generates more engagement than other types of content.
Algorithms determine what content to spread based on metrics like engagement – how much users are liking, commenting on, sharing, etc. a piece of content.
Misinformation tends to generate more engagement than other types of content.
Saying something outlandish and inflammatory, but untrue, is likely to generate more comments, etc. than saying something less divisive or extreme but based in fact.
This is exacerbated by the fact that any attempt to correct the misinformation will still register as engagement.
See also https://dl.acm.org/doi/full/10.1145/3616088