Any insight on what may cause the Challenger to be unable to unstick?

Avweb has reported that the pilots stated to investigators in this crash
and the last Challenger crash a few months ago in Colorado that they
were
unable to pull the stick back during takeoff.

Hmm. But they were able to do so when performing the flight controls free
and correct checklist item?

The bull****ometer is starting to peg here....

So, after reaching v1 and not being able to rotate, they just looked at each
other and lit up a cig and crashed, is that it? I think it was probably a
little more complicated than that.