Last election was one of the active ones. The people who didn’t participate are roughly those who never do. If the prospect of one more Trump presidency didn’t motivate them, they are truly, totally non existant as citizens and frankly as members of society. Their voices exists only as an annoying buzz on social media, and their opinion don’t matter, newer were.
You assume that those numbers are people who are left leaning, but as the research from the last election cycle showed, almost 80% are either consistently voting or consistently don’t, and the rest are roughly evenly spread.