not necessary?

A bit of a possible plot hole occurs to me, although I am not really qualified to pick at it as my video machine decided to stop recording after 1hr 38mins, (I was watching with adverts - I know the runtime is 87 mins) so I missed the end. However, assuming the mission was successful and the villains were dealt with, which is what I am assuming happened, it would not have been necessary for our hero to go back in time to sort it all out, as it (now) was all sorted out at the time. I suppose he could have tried to go back earlier to save his dad, which should have been easier as he now knows who the killer was, oh dear, my mind is beginning to spiral out of control!!! Time travel does this to me. Be happy.