??

Yes the asshole brother is dead thankfully in the current timeliness. Right now it's talking about the past.

Why is he dead?

There isn't much information on why he is dead, but most likely it was either a. Intentional, b. Accidental or c. All of the Above or d. Something completely different.
My guess is that he's such an asshole and brought ML down so much that something happened in which caused his death. And as in the last chapter that has been released ML is planning to use Yeongwoon to get rid of him. Me and others are thinking through that plan ML fell in love with him. And then since asshole died, the family paid Yeongwoon's family in season 1 it showed, and that was a big thing of Yeongwoon's anxiety especially as he fell in love with ML, I don't know if I'm getting it all correct, but based on what I've read and known that's what it seems like. We will have to wait for future chapter to know why the asshole brother died lmao.

A really good thing the SHIT brother now is dead

We can all agree on that