Isn't that a huge problem? Who picks their leader because he is entertaining?

Nobody, but maybe it's a similar phenomena of how people choose brands. Where, people tend to buy brands they recognize most, even if they don't actually know much about said brand or it's quality.

Trump was the name on everyone's lips. Could it be possible that introduced an implicit bias in his favor? Is this a case of "any publicity is good publicity"?

Every US presidential election is baseline 50/50 and ends up decided by a small number of people who are as fickle as all get out and dumber than dirt. They don't vote for anything recognizable as a "reason."

It's not that. Maybe some voted based on entertainment value but it was an ad hoc alliance of:

People who only ever vote GOP

Pro lifers

People who thought he was somehow being unfairly prosecuted for Jan 6 and having crates of classified documents in his pool house

Podcast listeners (people who are heavily influenced by Joe Rogan, Tim Poole, and the like)

People who are ideologically aligned with Stephen Miller

And, drumroll...

Centrists who believed the GOP talking point that Biden was the sole or primary cause of inflation. To their discredit, the dems seemed to have no interest in refuting it.

Dems seemed to be running on a platform of "We're not Trump". That was enough in 2020, after four years of Trump. It was not enough in 2024, after four years of Biden.

Also, Trump just had to say "I'm not Biden".

Which shows how remarkably easy it is to manipulate the American electorate.

There are no simple explanations in this arena. All campaigns min/max messaging for sought after demographics to maximize votes. One could argue that the collaboration brought on by Elon/X gave the Trump 2 campaign some of the most sophisticated frameworks for data driven, atomized political messaging/monitoring ever seen in federal electoral history. That is a monumentally effective effort to convert and acquire voters-- I advise avoiding such simplistic explanations, especially when they double as thought terminating cliches.