The gist of it seems to be that for some reason number 4 engine started to produce full thrust with the thrust lever at maximum power after landing and no one noticed. Interestingly, the thrust reverser on that engine was inoperative that day (MEL allows dispatching with that fault).

Pilot error? They had to use a non-normal procedure because of the broken thrust reverser and messed it up and the number 4 thrust lever was never brought to idle? That would make sense but doesn’t explain how the thrust lever ends up at maximum power after that.