You're happily married and you and he don't have anything in common anymore.
I'm sure your husband wouldn't like you having chat sessions with another man nor would he want you hanging out one on one doing date like activities with another man either even if you DO say its platonic. For sure he wouldn't care for you doing any of the above things with a man you clearly had some kind of infatuation/lust for.
Yes. Stop reaching out to this guy and if you happen to see him on the street say a friendly hello and then keep moving on. He's a part of your past now so leave him there.
Why he stopped the friendship is irrelevant.
“The willingness to accept responsibility for one’s own life is the source from which self-respect springs.” ~Joan Didion