If you look too deep, you’ll fall in.
The current characters making their way towards their do… to the Temple, are not the original heroes. It’s not that there was a TPK1 (yet), it’s more that, due to RL Player shifts, a new group of characters gradually worked their way up in level to where they could handle to challenges posed by the Temple… and the DM decided to mess with their minds.
Suffice it to say that this is not a standard dungeon crawl campaign.
“I shall return.” DM
1 If you don’t know what a TPK is, stick around.