During Trump’s presidency, Hannity has mentioned his 2016 opponent on 86% of his episodes
And why would Hannity be doing this - still?
1) he's really honest
2) he wants what is best for the Democratic Party
3) Hillary is a current candidate for public office and she's on the teevee like all the time, thus she's really relevant
4) ideologically, his preference is for real progressives
Or perhaps not. What he is actually doing (along with many others at Fox and elsewhere) is continuing to capitalize on decades of slime from rightwing media and politicos that quite effectively colored the impressions of many Americans about Hillary. No other figure on the left has been as demonized as her. "Lock her up".
In marketing, this technique is called "positioning" - the attempt to convince people that X is intimately tied to Y. Buying a Mustang will get you in bed with hot women. Ex Lax = Niagara Falls. Coca Cola leads to world harmony. Palmolive dish soap will make your hands softer and prettier. Etc etc.
Those are positive examples. But the same technique is used to encourage people to think poorly of something or someone. Take pretty much any Fox or Trump comment on immigrants from south or central america - drug mules, cantaloupe thighs, murderous, terrorists, thugs, etc. Or the famous "daisy ad" of '64 that damaged Goldwater's run. Etc.
Because the right wing base (and others) were so effectively propagandized on the topic of Hillary, she still has great utility for people like Hannity who are out to keep the Trump base angry and stupid.
Edit: ps... I ought to have noted that this is pretty much the same playbook that the right is using against AOC. They have been, and will continue to, demonize her because she represents an electoral danger for them up the road.