More Catholics in Vietnam

Catholics represented the bedrock of support for South Vietnam, especially in the Diem era however they were only about 10% of the population, and many of them where refugees from the North.

What if instead of 10% we double or even triple the amount, would having 25-30% of the population back South Vietnam come hell or high water save South Vietnam?
 
I would imagine the PoD required would butterfly OTL Vietnam War away and may require a pre-1900 PoD, but I am certainly not an expert.
 
Well, the Vietnamese emperors in the XIXth century (post Gia Long) were extremely anti-christian. Violently so.

They thought it was a challenge to their rule for various reasons I can get into if you wanna but among them, fear of western inference.

Their persecution was the main reason why they got invaded, talk about iony...

If relations with Gia Long in his later life were better or if Tu Duc wasn't as persecutive, you'd get more Christians, the conversation rate was similar to that of Japan
 
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