In essence, the party is stupid. Both are, obviously.
And... this is exactly the problem. People together are supposed to be greater than the sum of us. But we see exactly the opposite. We discard our intelligence in favor of much simpler institutional and cultural algorithms, which fail us repeatedly. Extremely frustrating.
The reason you haven't heard of it is the reason running against your own party's encumbent President is historically a bad idea.
For Joe Biden? Absolutely. For the other candidates? There absolutely is a point.
For the party as a whole? Depends on what they want. Do they want the best candidate they can get? Or do they want their preferred candidate to be undamaged?
(And why should they tilt the scales in the direction of a "preferred" candidate? Arguably, it worked for them in 2020 - they avoided a messy primary that would have weakened whoever the candidate was. An unweakened Biden then defeated Trump. But in 2016, the preference for Hillary - or at least the hard feelings caused by the shenanigans in her favor - arguably led to Trump winning.)
"Let's see if we can get a Biden sequel going in, if not, maybe we can use other existing IP, like a Kennedy. What other things are popular now? Women! Oof, Hillary in 2016, though, that underperformed at the box office..."
Also, the narrative that Hillary Clinton somehow failed spectacularly is a retrofiction. She got millions more votes than Trump, it just didn't actually matter because she didn't campaign well enough in the correct states.
No, computer software, rocks, old shoes, and other things that aren’t people cannot run for the Presidency.
You don't lose your citizenship when you leave the country. You'd have to give up your American citizenship somehow, like Boris Johnson did. Hmm...he could actually move back here, become a US citizen again, 14 years later run for president, and be the first one to have lead both the UK and the US?
Edit: he just needs to have lived in the US for 14 years, not have been a citizen for 14 years. He would still probably need to re-establish his US citizenship before running (but the constitution isn't exactly clear if a natural born US citizen but not a US citizen now can run for president after living in the USA for 14 years; its unlikely to ever come up anyways).