ALL OF THESE ARE SPOILERS STOP READING IF YOU’RE THE KIND OF JACKWAGON WHO WHINES ABOUT SPOILERS.
Thanos did it all just so he could go camping. We joke a lot about Thanos being a dad, and doing things for dad reasons. He wants half the universe gone so he can get some peace and quiet. His clothes suck. They just do, because he is a dad, and because it’s hard to worry too much about fashion when you’re an Eternal. He even has sketchy friends like a dad. See: Ebony Maw, the kind of sketchy dad friend would totally ask his buddy’s eight-year old to borrow some money, and then taunt them too personally after whipping their ass at Fortnite.
