In my opinion, Hercules and Megara went to Mount Olympus because Hercules was Zeus's son, and Hook was there so Zeus could tell him he gets to be alive again. There is a different Better Place, where everyone else went to. Also, in the Greek mythology The Underworld and Mount Olympus are based on, Mount Olympus is the home of the Gods, not the good afterlife.
I was just saying that since Mount Olympus isn't traditionally at all part of the afterlife, the Better Place might be somewhere else, with whatever that person's version of paradise is, while Mount Olympus is just where the Gods are, and almost no dead humans live there, the sole exceptions being Megara and Hercules since Hercules is Zeus's son and has been ascended to being a god. And when we see the Better Place everyone else goes to, it doesn't look like a mountain with Greek buildings on top. If it's based on Hercules, then the Underworld would be the only Afterlife, with no Better or Worse Place, and Mount Olympus would just be the home of the gods, which of course isn't true. I would also like to suggest the possibly that the actual Better Place is being reborn, though this theory still functions without that.