Behind Robert Downey Jr. and the Russo Brothers’ Mega ‘Avengers’ Paydays

One reason is when behind a mask he can act differently to stark and still have fun in the universe

Another can be they're doing something akin to a variant of stark being that universe's dr doom like in the comics.

Business reason will be that marvel like working with rdj and he likes working with them.

It genuinely makes absolutely no sense...

Dr Doom is Romani and it's a major part of his motivation as a character. Taking him away from his culture fundamentally changes who he is!

There are now FOUR Romani characters that have been white washed in the MCU at this point and it's starting to feel like they are purposely removing the Romani parts of these characters in order to sell the films in areas that are racist towards the Romani people.

This is also the second time Marvel has cast a Jewish person to play a Jewish character (the first being quicksilver who dies in his only movie) but only AFTER making Wanda (the daughter of Magneto, a Holocaust survivor) into a Nazi that works for a Nazi organization.