I don't think it was the sole reason why Crabtree came to the table, but I think it's a combination of things.
1.) The 49ers made it clear they weren't going to cave.
2.) The 49ers filed tampering charges against the Jets. This was sure to scare off any team who was talking to Crabtree in secret. Potential teams interested in Crabtree withdrew their support.
3.) Crabtree was very likely to drop in the 2010 draft if he held out that long, especially if no teams could interview or hold a workout.
I'm sure the good record and play was a small factor, but not too much. I think it was the fact that he lost all of his leverage in negotiations, I think. But it didn't help that the 49ers were doing well. If they were doing poorly, he could've been like "See! You guys need me! So pay me!"