>>109024844I'm not into him but it likely has to do with his personality.
He's very energetic, simple, temperamental and somewhat crude which makes him entertaining. At the same time he's highly incompetent and pathetic so even when he's being an asshole he's the one who ends up suffering from his actions. It makes him very childlike which can be seen as cute by some people.
His face is very expressive because of his huge cartoonish eyes and in general his design is pretty simple so you can easily imagine him as a human guy if you feel like it.
If you have some time and are curious about it you can watch Osomatsu-san sometime. It's an /a/ show about six Japanese Master Shakes which is somewhat notorious for its adoration by female anime fans.
