It’s easy to forget that US political parties are not actually the government. They’re just people who get together for common purpose, like a book club or a softball team. Those parties can run whomever they want in their primaries, and the states have no role until it gets to putting people on the real election ballot. At that point, if someone puts in their name and they’re too young, not a citizen, not a human (looking at you Idyllwild), or otherwise ineligible, it becomes the job of the state not to put them on the ballot, regardless of whether they’re sponsored by a party or not.

I agree. He shouldn’t be. But that doesn’t mean lawyers and judges agree.

the ballots and election process are largely left to the states. (Baring violations of the CRA, etc,)

Keep in mind, at the moment, it’s state supreme courts and their rules they’re voting on (as deciddd by MN Supreme Court , recently. The judge made a very wink-wink-hint-hint note in his ruling saying it “may” not be the same case in the main election)