What is the reason for this unusual flight path?
My guess is the captain requested and the dispatcher approved an excessive amount of fuel to deal with the crossing of the long line of weather.  The flight plan would have to reflect being able to burn off that excess fuel to be able to land BELOW the maximum landing weight of the plane. The crossing consumed far less fuel than expected so the crew had to burn off the excess fuel by flying the filed flight plan.  Or they could have just wanted to fly the filed flight plan because flight crews get paid by the hour and they would have just about doubled their pay for that leg.