Well, people building/buying Wagner's busts are some big fans of his music who want somehow to materialize their fandom.

They certainly are not fans of his life, his life is extremely irrelevant, it may as well be totally forgotten, and it would not hurt.

About your last edit: here I beg to disagree.

I love his work as a filmmaker, it made me love the sea and nature in general and made me want to protect it. When I was a child he contributed to educate me and make me an environmentalist. On me at least, his work was tremendously successful.

As an engineer, he created a lot of devices used today for diving. His boat Alcyone was even sporting revolutionary static turbosails.