No need to have two tags for the same thing.
I am somewhat indifferent which of the two tags should be used, but since by now, one of the two tags clearly won in terms of popularity, I’d stick with that.
Reverting that would only make sense if there are strong reasons why attraction=maze would be a bad idea, and I am not aware of any.
That the adoption was significantly boosted by iD is an interesting fact but ultimately this lies 5+ years in the past and already before that, since 10+ years attraction=maze was more popular that leisure=maze.