He's chocolate milkman now
Well, yes, this guy.
But with all seriousness - as you correctly stated, he is average. Normal. Like the most normal looking character in the game - he doesn't have oversized lips or exaggerated chin, or inhumanly wide smirk, or a face shaped like a brick, or even brightly coloured hair, or heterochromia. And that's what makes him more appealing in comparison with other neighbours - the way he looks most human among other humans.
Also, many in the fanbase loooove the 'tired stoic man who needs some loving and caring' trope, and Francis is the perfect embodiment of that. He is also a bit blank personality-wise, so it leaves a lot of room for fantasizing.
And he's kinda cute. Clear and nicely proportioned face, calm demeanor, implied stable job, sooo... Why not? It's fun, let people have their fun, have some fun yourself :D
Alright I might get hate for this but I truly do not understand this simping over milkman. More specifically how the simping originated. I mean let's be honest ppl this guy?
This guy ain't hot. Now the fanart? That's a different thing, simping over his fanart I get cuz I mean come on. But like, this guy is literally the only normal looking character in tnmn and ppl start sexualizing him. Why? I'm open to arguments of course so comment down below as to whether it is this person above u simp for or the fanart, also if u do then why? I'd rly like to know that.
Also hey I love tnmn so no offense, although that doesn't make a lot of sense.