Why didn’t Flynn simply clam up, take the hit and wait for a pardon from Trump?

Considering Trump’s penchant for lying and for going back on his word I sure as shit wouldn’t trust him.

Flynn knows he has better chances with a room full of Komodo dragons, or escaping from the rancor’s pit.

Because as soon as he gets pardoned, he isn’t in jeopardy and can be forced to testify under oath, and cannot take the fifth.

I would be surprised if the possibility wasn’t discussed. Their lawyers were collaborating on the case for a long time.

I guess he got a better offer, or more likely, a stronger promise. Assurances that someone will take care of you don’t go very far if they won’t commit publicly or formally with some sort of contract. The plea agreement in front of him was a sure thing.

Maybe he wanted to side with the good guys.

Maybe he blames Trump for firing him and is out for revenge. Keep in mind that Flynn is widely regarded as being a bit of a flake.