Reread what I wrote. I DID surrender. And even those that fled couldn't outrun a freaking dragon. I think you'd understand better if you read what I wrote
This is what you said;
Then it all fell apart. Thinking battle was imminent the drow rogue pulled back her bow and shot. Knowing us low level PCs wouldn't have a chance, I tried pleading one last time
Note here you said the drow started combat? So who's fault is that? The drow's. No one else's.
Yes you tried pleading again, good move. You failed again, so that's two rolls and I guess you got eaten for your troubles, bummer, but fun if you imagined it that way. What did everyone else do? Fight, surrender or run away? If they fought, well then they got what they should have.
The Vault is full of columns, small spaces and places to hide, so sure, they dragon could come after them, but in a single round they probably could have gotten back to the stairs, which the dragon would be too large to climb as a dragon.
Look,we don't know all the details, maybe your GM had the dragon in dragon form chase the players back through the vault and hunt them down, you didn't say. But whatever the case, it still not a single roll that caused the TPK. Maybe a roll put your group on that path, but even more than that first 1, the drow's decision set the path, that's not a roll, that's a choice.
I hope you all had fun, TPKs are, imo, chances for a great story. Hopefully you will all have this as some sort of lore in your future campaigns, or at least an inside joke ("don't let the drow carry a bow!")