From what I've seen about this incident it looks like the flight attendants took it upon themselves to manually deploy the O2 masks and also initiate the ground evacuation.
In one of the videos a flight attendant can be heard yelling "BRACE, BRACE, BRACE" at the top of her lungs during landing. Really? Where did she get the idea there would be anything other than a normal landing? Normal as far as the plane landing in a normal manner, albeit with a single engine.
It sounds like one or more flight attendants completely overreacted to this emergency and caused the passengers to think they were in a much worse situation than they really were. Possibly the purser or the lead flight attendant since they are usually the ones to set the mood for the rest of the flight attendants.
An engine failure with a blown oil seal makes a lot of smoke, but once it's shut down it's not a big deal. It's just an engine failure and a single engine landing.
I'm kind of wondering just what kind of communication there was between the flight deck and cabin.