Computers Blundering

I've been playing unrated 15/10 games against the computers.  I started with Computer 1, and worked my way up to Computer 6, and lost about 10 games in a row, until it blundered and gave away its Queen, and I finally won.  This Computer 6 (Komodo) was kicking my ass and now I've won 2 games out of the last 3 because it's made stupid blunders.   I'm wondering, are these computers programmed to blunder on purpose like that?   I didn't know a computer could make really stupid moves.   I'm the one who blunders all the time.  Not the computers.  What the heck.  I'm happy to win, but it's weird, the computer acting like a human or something. 

When engines are set to a lower level, they will randomly blunder, which ic supposed to represent "human" play.