I'm glad to see this guy go to jail, but it's not clear this was terrorism. Terrorism isn't just "terrorizing people," it needs to have a political component. There doesn't seem to be an indication of that, at least in the info available.
https://abcnews.go.com/US/subway-shooting-suspect-pleads-guilty-federal-terrorism-charges/story?id=96116527
https://abcnews.go.com/US/subway-shooting-suspect-pleads-guilty-federal-terrorism-charges/story?id=96116527