had to have been vs. has to have been vs. must have been
The speaker is speculating about something in the past (so basically it is a past modal here, meaning has to have been is irrelevant) and there is different degrees to speculation indeed. Had to have been is stronger than must have been and might/may/could have been is the weakest of all. Must have done means it's almost certain that something was the case while had to have done means it's very certain that something was the case.