I think it is caused by @erkan no longer moderating the hangouts. He has some good people talking skills to make the hangout more interesting, also in terms of guests.
Another factor might be lack of recordings. Many people can't attend so they reach for recordings. When they see that the last was from half year ago, they assume there are no more hangouts.
Another thing might be Steemit limitation. I would like to resteem the RSVP post, day before the hangout, but can't as is is too old.