Some adults try a bit harder to live up to the ideals of being an adult than others. They are toddlers inside like anyone else, but there's a layer of restraint on top that evidently not everyone has.

that's a millennial (and up) american pov

I assure you other cultures will be deeply offended if you imply 'there are no such things as grownup' (which sounds like a weird affectation to my east european sensibilities)

I agree to a large extent. Yet, what we see going on in US political leadership truly is beyond my belief of what reasonable adults should do and act like, even as an (precocious, sharp) ex-child.