Can someone please give me some insight as to why so many people are glad she's dead?

I'm very new to trying to understand a lot of politics. I just told my dad I saw the news and asked him why this might be a good thing (he is a yuuuge Trump supporter, has been since 2015) and he said that he has massive respect for RBG. He had no idea why you guys might hate her.

I'd love to know some things to look into so I can try and help my dad see some stuff he might not know about, too.

Thank you!