I believe it was a good and pretty obvious fold. The board was extremly dangerous and you had only committed 5,000 to the pot and his bet was for another 25,000.
I think he may have had a

on the big blind, and he may have made a poor call pre flop. He may have hoped you had hit a flush or Aces or Kings so you would call. He was not scared that you had a

because you checked the turn. If it was a bluff, then fair play to him, he made a massive overbet and will lose a lot of money in the long run playing like this.
BUT you won't, its a fold everytime.