Because Tancredo ran away from his own proposal when Pence took it up.
When it was offered by Tancredo the bomb thrower, that was all right. But when Pence took it up, it suddenly looked as if it might actually pass--and that would leave Tancredo without an issue to run on and raise money on.
I think that Tancredo enjoyed being a cult Congressman, the favorite of a small amount of people. When he's faced with the possibility of getting something done, I don't think he wants to have anything to do with it.
What is your problem with Tancredo? You have a problem with someone speaking the truth about immigration?