Paying large sum before exchange?

[solittletimeandsomuchtodo]

Why??
Three in the chain. Middle vendor has paid a significant amount of money yet the buyers for their property have not even exchanged with them yet.
Bank survey not even booked so it could all go pear shaped and they will lose this money paid.
Is this not the dumbest thing ever??

Are you involved in this chain? Does their reason for paying this money have any effect on you?

Perhaps their ability to purchase is not dependent on the sale of their property and are (loaded) able to proceed even if their buyer drops off a cliff.