Gary Hart hates campaigning. It’s half the reason why he ran for the Presidency, he was sick of kowtowing to Colorado voters way too the right of him, with the other half being he really was (often) the smartest guy in the room despite his massive blind spots (sup a long tangled web of military reform, women). So he figured he should be President to deploy his ideas so his Senate colleagues and Reagan couldn’t stop him anymore. Think liberal Nixon without most of the bad parts, but also without Nixon’s willingness to makeover himself completely for 1968.
“Where’s the Beef” was hilariously effective and also completely wrong, as Hart had easily the content and policy ideas of Mondale.
So… did Hart have the best chance of any 1988 Dem to beat Bush? Yes. Easily. But he wasn’t a good campaigner. Bush wasn’t great, but he worked for it like he did in 1980 and hired the people that would get him to the Presidency whatever the cost.
Edit: the Dem base wants to fall in love with a young dude who loves being there in front of them: JFK, Clinton, Obama, Beto.