Why did Daniel drink the Amnesia potion?

[Tanshaydar]

They just never attacked him?
And so I'm guessing when Daniel left, Alexander told them to kill him if they found him, right?

That makes sense. Was this part explained in the game? I must've missed it.

Some notes, Daniel and Alexander mentions them. If you remember the scene that you were caught up, that is where Alexander told them to catch and lock you.
Otherwise, it's likely that their aim is to kill Daniel.

But when Daniel and Alexander were working together, they served Daniel too.