Deploying the mask, pilots must probable avoided pass affected by smoke. It was a very good decison.
no, the masks don't prevent smoke inhalation, they simply add oxygen, not ideal if there is a fire in the cabin.
Please take a look in this accident report at the possible cuase for fatalities. Note it was a an engine fire on ground!
if this was the British Airtours incident at MAN, then the smoke came from outside the cabin and the fuel fire rapidly spread, so no real relevance to this situation.