Speaking of those “fine” Republican candidates in 2016, they were all flawed and those flaws were up front and center. Consider:
Jeb Bush - too close to his family, pro-immigration neocon, had no energy of his own
Rubio - neocon and part of the Gang of 8 that made the immigration deal with Obama. That pro-immigration stance incensed much of the base of voters in the primaries hence he never got traction.
Cruz - neocon, he did not come off well in the debates
Kasich - another pro-immigration neocon
I could keep going but one should get the idea: a substantial number of Americans no longer wanted the “forever” wars that were and still are an integral part of neocon policies. Sanders was the candidate who espoused this view among the Democrats and he scared the pants off the DNC before finally stepping aside for Hillary. Trump was the only Republican candidate to espouse this view; no other Republican candidate would go against the neocons.
If one wants to vote for Biden, that’s fine, but Biden voters should understand they’re approving the neocon agenda. Because it will return big time to the forefront after having been held back somewhat by Trump since 2016. Democrat voters had the chance to say yes to the anti-war faction, but they turned their backs on Sanders and Gabbard. So be it, they made their bed, they can lay down in it. Like the Trump voters are doing.
One has to look at what the American voters wanted: more control of immigration than was present in the Obama, Bush and Clinton administrations, and an end to the foreign wars. Those were Trump’s major platforms in 2016. No one else argued for them in 2016 like Trump did. Now it can be argued whether Trump was effective on those points, and whether Trump can run on that again. But given what many American voters wanted, Trump’s victory should have not have been the surprise many think it was. It was an attempt by voters to send a message to the elites who run the country, many of whom are never-Trump neocon Republicans who are working as hard as they can to undermine him. Who have even threatened their own version of “cancel culture” to go after Trump supporters and administration figures. To continue even after Biden’s victory so they can make sure that Trump voters never ever get their way again, even for some other candidate.