Why did everyone try to same things?
Everyone tried to kill Arthur. All of them failed (maybe, just maybe, there was a pattern emerging and they should try something new).
Everyone tried to take over Camelot (and that was failing just as badly. Please get a new hobby.)
Everyone tried a dramatic speech when they tried to take over (and that gave Merlin plenty of time to stop them, somewhere about the two minute mark).
And everyone tried poison. Morgana, Nimueh - even Merlin himself. (Please stop. It was normally Merlin they were trying to poison, although he hadn't managed to poison himself - yet.)
