Narcissist, certainly; immoral and corrupted, most likely; but still possibly rational [0], I see no reason they'd be de facto irrational despite how I feel about them. Born autocrats (or born in a line of succession) are a different story, but I'd argue it would even be unlikely for a commoner to ascend to absolute power without starting off as a rational, calculated and intelligent person (tho ofc not impossible, there are obvious cases). Not that there is any guarantee they'll necessarily remain so, seems unlikely after years or decades being surrounded by sycophants.
Feel free to disagree.
0: https://www.oxfordlearnersdictionaries.com/definition/americ...
Survival breeds sycophants, ...
Shit, why am I reciting stuff from 8th century BC here?
I think we agree on that.