Pretty sure it’s cynicism ;) It’s a recursive game, really, you can play it forever.

Like, why would you choose to believe that happiness is believing the lie — especially if you don’t think it matters which one you choose?

I never was one, so I might not get it, but couldn’t a nihilist just choose to be happy, since it doesn’t matter to them anyway?

But regarding cynicism: https://medium.com/@ngoeke/the-4-isms-that-ruin-your-life-b839548ef9a3