Why would a rival wait in that instance?
If you need it explained you'd never understand anyway.
Same reason Ullrich waited for Armstrong
Completely different situation. A spectator felled Armstrong not a botched gear shift. Contador didn't attack him either. He carried on at the pace he was already setting at the time to catch him back as he'd been caught napping at the back of the group.
I don't disagree that it wasn't a nice thing to do but he's got 2 other riders to worry about who appear to be getting stronger and they didn't wait either.