What would have happened to Christianity if the temple had continued operating?
If the temple had continued operating, Christianity would never have gotten off the ground. The temple and priesthood remained viable, creating profound Jewish opposition and the only place to worship. God therefore had the temple destroyed and the priesthood uprooted so there was no temptation to hold to temple worship.
Les teaches that if the temple had kept right on operating, Christianity would not have gotten off the ground. There would have been profound Jewish opposition because the temple was still viable and the priesthood was still viable, and it was considered the only place to worship. God knew this, so He had the temple totally destroyed, the priesthood uprooted, and Israel sent out into the nations of the world. That removed any temptation whatsoever to hang on to temple worship. This is what Paul comes back to: since the death, burial, and resurrection, and since the revelation of the gospel of the grace of God, henceforth we do not know Christ after the flesh. We are no longer going by the things He taught to Israel under the Law.