Slater was never David's past son...

He was copying Greg!
Because of a sum!
Melissa had instructed Slater and Derek to mess up with David Mayer's past kids...
To steal their sum.. the cult has no fund. They stalk people and kill... latter they steal their sum... why God released the 4th horse to kill those members in cult.
There is no fund there. They will just instruct to heist!