That’s basically it. Romantic obsession can look a lot like mental illness, and definitely feels like it. Being charitable to the guy, he might look back on this and wonder what the hell was going on in his head.
I know I’ve been through a breakup that nearly killed me, and sheer white-knuckling restraint is the only thing that stopped me acting like this. It’s like a bereavement, but you also know the person is twenty minutes down the road.
Or he might have been like this through the whole relationship, who knows.