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.
Very well said. I've started a few month ago on an AI/Bot for 0AD an open source game. Scripting language is JavaScript running on SpiderMonkey. So far I've accumulated thousands of locs, learned a lot about writing fast code against a specific engine and have barely more than a framework. But I still remember the moment the bot did it's first baby steps and actually build a structure to train some scouts and started exploring the map.
Also it became a decent exercise in dealing with abstraction. The code base just explodes if you do not follow DRY - strictly.
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).