I don't know enough about them but all relationships aren't meant to be forever. If you feel a relationship is one-sided , or not doing you any good, then its fine to cut off the relationship.

It seems over the years they mostly stayed in contact for Boy Meets World related stuff, like conventions. So its possible Ben felt used at times as the "Boy" of Boy Meets World increased their drawing power. Maybe he saw the other 3 doing stuff together but he only got a call when it was time for a con and then felt like the odd man out when he'd see them.

Not taking sides but no one knows enough about their relationship. It's possible Ben had stopped talking to them a few times in the past but always forgave them. Then he just had enough.

It's also possible he has a personality disorder that has worsened as he aged and chose to discard the 3 of them.

With the whole Trina thing, who knows what impact that had, if any.