Great article, but I think you’ve missed one significant difference between Sanders and Clinton. The argument of the status quo. In 2016, Obama was the president and Clinton represented a continuation of the status quo — it’s easy for voters to examine what they have just experienced and either accept or reject the status quo based on whether it feels like it’s working.
What Trump did, whether skilfully or just as a result of his bombastic style, was sell an alternative to the status quo that captured the imagination of enough voters to secure him the Presidency. All Clinton could offer was to be a continuation of Obama — with all the inherent stability and (argued) neo-liberal corruption.
Trump must now defend the status quo — which is currently absolute unmitigated chaos — against an opponent who doesn’t need to be anywhere near the strength of opponent required 4 years ago. If Clinton and Biden had reversed roles, Biden would’ve lost in 2016 and Clinton would’ve likely been the president elect in 2020 without much of a struggle. It’s less to do with their gender and everything to do with their timing.
The ‘female president’ card was played too early — the backlash against Obama needed to play itself out into the epic narcissistic toddler-esque shit-show it has inevitably become. The political left is always committed to shooting each other on the carousel of identity politics — on this occasion, they’ve managed to shoot each other in the wrong order. Without Clinton 2016, we’d now have Warren 2020 and the USA would likely be a much safer and more stable place.