In the end this may have been the only compromise available to Pelosi. She couldn’t force him to resign and his allies in the House may have resented any attempt to make him do so, knowing that it would have appeared as though he was stepping down in disgrace. Which, ah, he would have been.
So Conyers gets to finish out his two years, leaving on “his own terms” replete with plenty of pomp and circumstance in the House about his glorious legacy, and then he’s gone. And in the meantime Democrats get to cross their fingers and hope that there isn’t a drumbeat of new accusations against Conyers in the media over the next year that dilutes their “the GOP elected a predator in Roy Moore!” message for the midterms.