Question

why did the mariners blame the ancient mariner for their plight?

Answer 1

the Mariners blamed ancient mariner for their plight because they thought that it was deed of ancient mariner that brought fog and the mist.
the deed was that he slew the innocent albatross.
they also blamed him for the stopping of winds and also the movement of the ship was checked

Answer 2

mariners blame the ancient mariner because they were considering that the fog and mist they facing is because of terrible deed done by the ancient mariner by the shooting the albatross.