Push somebody over the edge
From TheFreeDictionary, pushing somebody over the edge is defined as:
If an unpleasant event pushes someone over the edge, it makes them start to behave in a crazy way.
Can crazy here be to mean all of the following: non-sensible/stupid, very angry, and mentally ill/insane?
Pushing somebody over the edge alludes more to a loss of control which might then be manifested via anger, insanity etc. I'm not sure that stupidity is necessarily associated with it. But I suppose irrational decisions could well be categorised under stupidity ...