The fires in the third building went uncontrolled for most of the day. Add to that that it was partially damaged from falling debris, and was probably as poorly fire protected as the other towers it seems reasonable.
The alternative is that you add the same variables as mentioned for explosives use on the other 2 towers to a third tower makes it seem even less likely. The lower floors were open and the building probably had a lower factor of safety against collapse than the other towers.
Is it likely that a third building would be rigged to detonate so long after the other two, especially with no plane hitting it?
I also don't think it looks like a controlled demolition. Normally explosives rigged on multiple floors on a delay so you collapse one section onto the one below. If explosives were used on it then it appears only charged on one or two floors lower down.
Good chance that the building would have suffered only partial collapse leaving the embarassing situation of explosives still attached to the building. It all seems highly implausible. (I am trying to be kind).