It wouldn’t have worked.
Evangelism only works when you live long enough to evangelize.
And any converts aren’t immediately killed for heresy.
Most early Muslims had BEEN Christians.
It’s a mistake to think they’re Muslim only because they haven’t been ‘evangelized’ properly. Arrogant and foolhardy too.
The history of the Moriscos in Spain would be interesting here. A subject of which I know almost nothing!