I'm going to wade in here and hope I don't get flamed. Hopefully if I say this, others will chime in with similar experiences.
Before I go on, none of what I am about to share should make you change your initial assessment of him as an absolute knob.
I am normal middle aged woman. Not particularly beautiful and I don't have men running after me.
I get these kind of texts and messages from married men on a surprisingly regular basis. The men could be coworkers or fairly close totally platonic friends or even blokes I went to school with who live on the other side of the country who I have not seen in decades.
I am certain beyond a shadow of a doubt that they are not interested in having an affair with me or really seeking anything at all besides a bit of entertainment and they feel entitled to my attention at any hour of the day or night because they are men and women are supposed to be flattered by every little scrap of notice.
When they are good friends, I might joke back for a short time. It makes me lose respect for them but it's not threatening and it happens often enough that I just think this is some knobbish thing some knobbish men do.
I do not agree with the idea that he would've tried to take things further if she'd responded. I do think he's a bit of a dick.
I have no idea what goes on in the confused and mixed up minds of men. I don't think they are always thinking much at all. They often women as just existing for their entertainment.
You yourself got at least one such message from another man. Did it really feel like he was trying to spark an affair? Or was he just being an entitled knob, actually, who felt entitled to your attention?