Here is my theory:
Elon was insulted by the diver. The diver called his efforts a PR stunt. But, it is easily argued that Elon sees himself as a humanitarian. So having his motives called into question, worse, having his motive proclaimed to be to capitalize on the suffering of children to promote his personal brand and the companies he has controlling interests in, is arguably the worst way to insult him. And, one could argue that from Elon’s perspective, it’s insanely absurd to make such an accusation.

So what does Elon do? He makes an equally or, perhaps hyperbolically more absurd statement that a man risking his life to save these kids and who has made a career in cave diving, is only in Thailand for their awful pedo sex tourism, something that should be obviously absurd, which should cause people to take pause and say “now that’s out of character for Elon, let me think about this…. AH! He is responding by doing exactly what the diver has done: making an accusation that he would be okay with children suffering just so he can get what he wants…” the absurdity of the accusation toward this diver should highlight the absurdity of the accusation toward Elon.

Now, in the public eye, this is not what was seen. But this is how folks like Elon think sometimes: very conceptually, and making unannounced parallels/metaphors/simile which are spoken plainly and expected to be spotted for what they are.

He is hyper intelligent and forgets most of society is full of morons. I’d you don’t get his tweet was exactly what I described and think he should apologize, then you don’t know folks like Elon.