Regarding those "nonsensical" aspects of RFK Jr.'s decision:

First, why Trump? You need to realise that Bobby's decision is not primarily driven by his level of agreement with Trump himself. Rather, it is driven by his sincere and passionate opposition to the Democratic Party and what it has become.

Bobby is more afraid of what a Democratic Administration will mean for the planet, the environment, and the kids.

Bobby is opposed to the neocons who want to drag us into WWIII. These are the ideologues who have been running US foreign policy for the past 20 years. Trump wants to break their grip. This is actually believable, because if you know Trump, you know he doesn't have an ideological bone in his body: he is 100% transactional - everything is a deal, and deals can change. He has never been a "true believer" in anything - unlike the people who would be advising a President Harris, who believe in totalitarianism, censorship and war.

So that is the play: not so much giving Trump a W, but denying the neocons in the Dem Establishment a W.

As far as not dropping completely out is concerned, this is done for two reasons, I believe.

First is the reason Kennedy gave to Tucker Carlson: apparently Kennedy's internal polling shows a tie in the Electoral College, with 269 going to each of the major candidates. In this case the third most popular candidate could be selected as POTUS. Apparently this is a long-shot, but it has actually happened twice in US history.

Second is just a hunch I have: by staying in the race, RFK Jr. could retain his secret service bodyguard detail.

Should have.

But no. As soon as he announced, the Biden Administration took away his Secret Service detail.

Always a classy act, those Democrats.