Board Thread:Sly Cooper film discussion/@comment-27370337-20160304234754/@comment-3349191-20160311065014

He most likely wanted to wait for the right time, the right opportunity to eclipse the family name to live up to that point, by feeding off of the hatred, and if someone from the present actually did had a hand in his immortallity than that's got to be the reason why:

Someone from the present travelled to that point to help with his immortallity in exchange that he would erase the Cooper line, however if he did so with any of the Coopers that came before Sly, his immortallity wouldn't last so he waited to get to Sly's time to be rid of him and than afterwards meet with his ally who helped with his immortallity so he or she could either upgrade it to last without the hatred or to find another target.