What would have happened to Christianity if the temple had kept operating?
Christianity would likely never have gotten off the ground. The temple and priesthood remained viable as the only place of worship, producing profound Jewish opposition and a strong temptation to cling to temple worship. God therefore had the temple destroyed and the priesthood uprooted so the gospel of grace could stand apart from the Law.
Les explains that if the temple had kept operating, Christianity would never have gotten off the ground. The temple was still viable, the priesthood was still viable, and it was regarded as the only place to worship. That would have created profound Jewish opposition. So God prompted the Roman army to destroy the temple, uproot the priesthood, and send Israel out into the nations, removing any temptation to hang on to temple worship. Since the death, burial, and resurrection and the revelation of the gospel of grace, we no longer know Christ after the flesh or follow what He taught Israel under the Law.