Why did God allow the temple to be destroyed and Israel scattered?
God allowed the temple to be destroyed and Israel scattered to confirm that the Law's era had ended. With no temple or priesthood, there was no temptation to cling to temple worship, and Christianity could grow without the profound Jewish opposition that a still-operating temple system would have sustained.
Les explains that in order to make it profoundly certain we are no longer under the Law, God prompted the Roman Army to destroy the temple. He asks what would have happened to Christianity if the temple had kept operating; he does not think it would ever have gotten off the ground. There would have been so much profound Jewish opposition, because the temple and priesthood were still viable, and it was considered the only place to worship. God knew that, so He had the temple totally destroyed, the priesthood uprooted, and Israel sent out into the nations of the world. This removed any temptation to hang on to temple worship. It connects to Paul's words that since the death, burial, and resurrection and the revelation of the gospel of grace, henceforth we do not know Christ after the flesh, no longer going by what He taught Israel under the Law.