Por que Hugo Weaving não reprisou seu papel como Red Skull?

Talvez porque ele não estivesse interessado em fazer isso. Ele foi bastante claro sobre sua opinião para o futuro retrato do personagem desde o início, de sua entrevista de 2012 de collider (ênfase minha):

I [signed a multi-picture deal] for Captain America. I think the tendency, with those films, would be to probably not bring a villain back. They might for The Avengers, but I didn’t think I’d be in Captain America 2 or 3. I don’t think Red Skull will be there. And it’s not something I would want to do again. I’m glad I did it. I did sign up for a number of pictures and I suppose, contractually, I would be obliged to, if they forced me to, but they wouldn’t want to force someone to do it, if they didn’t want to. I think I’ve done my dash with that sort of film. It was good to do it and try it out, but to be honest, it’s not the sort of film I seek out and really am excited by. As an actor, to do all sorts of different films is great. It stretches you in different ways. But, I increasingly like to go back to what I used to always do, which is to get involved with projects that I really have a personal affiliation with.

Mas nenhuma palavra oficial veio para Avengers: Infinity War especificamente ainda.

Em uma entrevista com a Uproxx , os Irmãos Russo foram questionados sobre Hugo Weaving não retornou e disse o seguinte:

Did Hugo Weaving not want to do it?

Joe Russo: You know, he made a statement a couple of years back that he was done with Marvel.

Parece que eles estavam cientes das declarações anteriores de Weaving sobre o papel, conforme mencionado na resposta de Ankit Sharma, e decidiram respeitar seus desejos de não fazê-lo novamente.

Por causa da dificuldade do processo de maquiagem envolvido, Hugo Weaving se recusa a reprisar o papel, apesar de se divertir jogando.