Let's be real here - Hillary has not been relevant for almost 2 years now. Yet people on the right still deflect to her constantly.
There's 2 reasons I speculate this happens
1. The right needs a boogeyman type figure to demonize and Rally against. Prior to 2015 this was Obama, and demonizing Obama did win them elections, and I guess it made sense in 2016. But now that she isn't in public office and won't be running again, it makes no sense. They should find someone else actually relevant to rally their people against. And no, she is not running again in 2020, that is nothing but a conservative wet dream because they know it'll be another easy win for trump
2. They're projecting. Since most of the right hails Trump as an infallible God like figure, perhaps they figure that the left feels the same way about Hillary. This couldn't be less true, most of us on the left, especially those of us far to the left, hate Hillary Clinton. Not only was she a garbage candidate, she lost what should have been an unloseable election. Her popularity among Democrats was never very high but its gone even lower since the election.