Hi, as a male and someone who is interested in linguistics, I've found that "himbo" is actually completely qualitatively different from "bimbo," and shouldn't be considered an insult at all.
"Bimbo" was typically solely used as a derogatory term. It meant someone who was entitled, lazy, overly concerned about their looks, and frustratingly dumb. Someone whose only redeeming quality was their appearance, implying that their sole worth as a human being was as a sex object. This was its original use, its current use, and only use.
Himbo, on the other hand, has weirdly positive connotations. From what I've seen, the stereotypical "himbo" is strong, conventionally attractive, and dumb, sure, but it's all spun in a positive light. A himbo is typically very compassionate, highly optimistic, entertaining, and often extremely capable (in areas that don't require a lot of brainpower). Himbos typically also are very aware that they aren't the sharpest knife in the drawer, and graciously step aside to let other, smarter people take charge when they need to. And when they do screw up out of stupidity, it's usually in a charming, endearingly silly way instead of frustrating. Basically, a himbo is a romantic fantasy instead of a demeaning insult: a strong, capable, and inherently non-toxically masculine individual who just so happens to be dumb as a rock. Which does give their potential romantic partner a bit of an edge in some areas, sure, but not in a way that degrades their humanity.
And what's more, a "himbo" causing problems is meant to be relatable, not demeaning. Everyone screws up, but the himbo screws up often, and in ways that are often unpredictable and absurd. Something that it takes an extra amount of thinking just to imagine how they could possibly have come to that conclusion. But they are always forgiven for these mistakes, since there usually is some logic behind their actions, even if it is ridiculous. And they always forgive themselves too, which is strangely empowering. In an era defined by anxiety and self-doubt, it's comforting to think that no matter how dumb your mistakes may be, they can always be forgiven if your heart's in the right place, and that it's okay to relax and not worry about unforeseeable consequences that are beyond your knowledge or control. It's okay to be true to who you are, even if who you are only has two braincells that are usually taking an extended lunch break.
tl;dr "himbo" is okay while "bimbo" is not because "bimbo" is an inherently dehumanizing insult and "himbo" has actually evolved into meaning a positive masculine role model, but dumb
This has been my himbo manifesto, thank you for reading