Building these AI's is actually a lot of work. They're usually built by a single or a few persons, in their spare time or perhaps as a college course. Most time is spent making sure your bot actually plays the game. Very little if any at all time is spent making the bot smart enough to deal with situations like this. In this case, obviously there's a bug where the bot is not dealing property with aerial attacks. A human player would have given up or made a suicide attack the second those mutas landed as he realized he missed a turret at his main.

Yes that was dumb. Should have basetraded (attacked with the tanks to force retreat (buy time and build towers) or destroy zerg base or 2 if the zerg keeps attacking).

I guess it was caught off guard and started panicking. Typical for human players as well.