The average person who never turns on the news has no idea what's going on and may have heard the initial report that Barr said no collusion, no obstruction (even if Barr didn't specifically say "no obstruction"). They have no idea what Barr's role is and assume he's just an impartial attorney general. Then the next thing they hear is that Trump was not convicted in the senate and therefore the impeachment efforts failed. So if you're that average person who doesn't watch the news from, say, Michigan, what are you going to think? "Oh, they're out to get Trump. Give the guy a break! I'm voting for him." This person has no idea of anything going on with the Southern District of New York and has not heard anything about what's really in the Mueller report.
Do you really want to lose that potential voter? To me the biggest way to get a voter like that is just continue to hammer home the facts of what the Mueller report actually said and all of Trump's other misdeeds, both as president and whatever else is being investigated in NY. And continue doing that until November and hope to hell that the message gets relayed properly to enough people. All the while reminding people about the shutdown (that's a story that I'd assume everyone heard about) and that Trump said he'd own it.
The big thing here is this has to remain in the news. You can't give Trump any openings to nationally claim victory with a real reason that he may get sympathy votes. Not getting impeached by the senate is probably the biggest way between now and then that Trump can pick up those votes.