Sam Altman-Backed Nuclear Fission Startup Oklo Is Going Public Through SPAC

I don't think this is a positive signal. Even in the 2021 boom, going public through a SPAC was still seen as what you'd do when you wanted to shift the bag to retail investors and were willing to take significant dilution vs doing a proper IPO. A bunch of companies with poor economics or differentiation did it to get out before their chickens came home to roost (OpenDoor, SoFi)

Seems odd not to mention that their application to NRC was rejected.

Didn't he invest tons of his own money in this or was that a different nuclear startup?

If he believes in nuclear that much, why not just help fund a plant with a proven design? It's much easier and it will help reduce the costs of future plans that use the same design.