See, this shit wouldn't throw me. As a DM I love improve in my plot lines. Hell, I often don't plan things out past laying out the world and enemy motivations.

Sure my big bad has goals, but they have to work for them just as much as anyone else does. One of the most fun (for me) campaigns I ever ran was where the big bad conducted a ritual off screen, and botched the roll. He ended up killing himself.

The party knew that he had been planning a ritual of some sort and had gone into seclusion. They had decided to dismantle his organization before tracking him down.

So weeks of fighting and taking out little hidden cells of the cult, they finally find info about where the big bad was doing his ritual. Only to find a mangled rotting corpse and a closed hell portal.

My DM once gave a BBEG speech without turning on a demon voice mod he was planning to use. He just sounded charming and made some really good points. Then he turned it on and it was a lot less convincing in the demon's "real" voice. We all got sudden insight into how cults of personality can work.

Don't give the party a choice you aren't prepared for them to accept 🤷‍♂️

Happened in one of our games too. It helped that the big reveal was we had been working for him the entire campaign already. Also it helped that the big bad was our king and not the evil advisor like we’d ‘figured out’. But he made some really good points, the gods were fake, they had abandoned us, we could execute the evil scientist on the spot. The only only cost was one city had to be destroyed in terrible torment, but then we could all ascend to godhood. But we would be gods, we could just cure them with our god powers after. The party was almost entirely convinced.

Except the murder hobo rogue who often didn’t pay attention to things, had attempted to kill a small child sick with a disease because we hadn’t found a cure(and failed though he stabbed her several times), and would spend his free time murdering people in alleyways during character down time(but only if he thought they committed a crime so it’s definitely not evil).

Our pet npc also didn’t want to so we were trying to convince him when the rogue suddenly tried to stab the king who, we already knew, could see into the future. The king did not get stabbed and the king’s bodyguard put the rogue in death saves with one attack. We were going to leave him there. But then the bodyguard turned to attack our npc for not joining and that was enough for us to commit regicide.

A player in my most recent session accepted an offer to become a vampire. I was settling in for a couple sessions of drama as I stacked more reasons for accepting the offer, nah, about 5 seconds in and they're ready for undeath.

And then what happened? Share the story OP.

Sounds like dune DBZ trash to me.