Kwesi Appiah put the hosts in front before Scott Wagstaff struck twice either side of half-time to leave the visitors with a mountain to climb. Substitutes Lucas Perez and Felipe Anderson gave West Ham hope, only for Toby Sibbick's late header to send the Premier League club tumbling out of the competition.
“It's very easy to explain what happened – it was one team who wanted to win and another team who played without any desire or any ambition to win or continue in this cup," the manager said.
“Maybe we thought we were going to win because we are a Premier League team and they are in League One, but Wimbledon played with the desire to compete in this cup. In the first 45 minutes, we didn't fight.
“We talked before the game that this game happens a lot of time where the team in the lower division beats the team which is better because they play every ball as if it is their last ball of the game. We didn't have that attitude and when we could, we didn't try.
“The pace of the game, the way we fought for every ball and the way we made movements to receive the ball were disappointing. I changed three players because I could only make three changes. I could have changed all the players.
“Unfortunately for us, they scored their third goal in the first or second minute of the second half, which made it very difficult.
“I repeat, we found a team which played every ball as if it was a final for them. I don't think they play like this in every game in their league but we know, in the cup, the weaker team can play as if this is a final.
“It's very frustrating because you can be eliminated, but not in the way we were. It's a disaster."