The series ended in a draw essentialy because of one move. The move 5. ...a6 in game 3 by the computer is very interesting/controversial. A computer needs to be programmed to play to its strength, i.e open positions. This move reveals a fundamental flaw in the program. The computer chose this even though 6. c5 is among possible replies which forcibly closes the position. So, the programmers did not incorporate best algorithms to avoid closed positions. Instead of 5....a6 why did not the computer choose 5....Be7 which is more in line with convention and less likely to lead to a closed position?
But, whatever might be the case, it was a good show by Kasparov. He showed that computer software has a long way to go more than computer hardware to beat humans.