Had to be for his pitching as he had to bat until 1973. Didn't know he was a switch hitter.

(probably not), Vida Blue was a pitcher. Being a switch hitter was incidental to being named MVP.

I wonder who the last switch hitter won the MVP for hitting.

Blue was TECHNICALLY the last one to do it, but it was the Mick before that.
And they were the only two:

https://www.yardbarker.com/mlb/articles/vida_blue_was_the_last_american_league_player_to_accomplish_this_rare_feat/s1_13132_38787438

Off the top of my head, Chipper Jones & Pete Rose

Only because one of the guys at the golf course asked it the day after Vida died.
I wouldn't have known it otherwise.
He went 24-8 that year with a 1.82 ERA. He had 24 complete games. His strikeout/walk ratio was over 3.4.
BTW: As a switchhitter, he only batter .118 that year which was below his career .133. Obviously, the MVP was about his great pitching.