So why did Evil Morty destroy the Citadel like that?

I get that he used the Citadel to rip open a hole in the Curve. Rick mentioned how he and Morty would not want to be there when it was done. That sort of makes sense.

But the tampering of the portal fluid and the tweaking of Operation Phoenix to liquify all the other Ricks and Mortys… What was that about? I don’t see how killing them helped.

While he wasn’t above killing, it seems like the writers wrote him as having a purpose behind it. They even go so far as to say it later on that he just wanted to be left alone.

So… why the mass murder? What did I miss?