They set the machine to play at 2-ply, i.e., it only looks two moves ahead. It's not so surprising even a good algorithm would lose in 15 moves at 2-ply.<p>The article mentions they also played at 5-ply and it lasted 27 and 30 moves against Kasparov, which is probably better than most casual players would do.
humans can look 5-8 moves ahead with practice. GM's can probably look 15 or so moves ahead as well as study tactics of regular positions such as openings.