Why don't people write out Hitler's name anymore? it is weird and childish.

I didn't know that is happening, but who are these "people" and why don't they?

Anyone writing seriously about anyone in history irrespective of what they did - will spell Adolf Hitler's name properly.

Just as they do for Mao Tse-Tung, Pol Pot, Josef Stalin, Saddam Hussein, their officials, etc., etc; however evil their regimes..

You have met most of these millions though? Methinks you exagerrate!

This maybe the strangest thing I’ve read on here.

I'd guess it has more to do with the widespread implementation of general censorship and various automated things. e.g. if you mention his name in a post or comment you're suddenly assumed to be either reactionary at an unhinged level (anyone you don't agree with you compare to him) or you're a racist nationalist trying to recruit people to your cause.

the same sort of things that make people invent words like 'unalive' as a verb to avoid getting demonetized in youtube videos as a 'violent' video.