He didn’t work many miracles there because of their lack of faith.
The Bible teaches us not to have doubters in our midst. In non-English Bibles, it says it more clearly as different terms are used for unbelievers and doubters. We also see that people were healed or had financial outcomes in modern times, when doubters were first isolated. People got healed as they left their home towns, not only when they arrived at healing crusades a few thousand miles away.
Do not be unequally yoked with non-believers.