He got caught in between decisions I think
Went for a normal slide with left leg extended, but saw Wells moving to block the plate entirely and curled his left leg up defensively, on instinct
It's was a horrible slide. Would have been better to just try to run through the plate and if you get tagged, whatever.
Really, it's revolting that a catcher is even allowed to do that. Other than whiny Jays fans nobody complained about the plate block. It should not be part of the rules for a catcher to receive the ball and then block home plate - and if it is then they should be fair game again!