this is overstated, it is currently placed as the third largest protest in America (in wikipedia at least, I've heard anywhere from 3-11M so numbers can vary), the two largest could easily be spun as political (George Floyd and Earth Day) https://en.wikipedia.org/wiki/List_of_protests_and_demonstrations_in_the_United_States_by_size
not dragging the accomplishment btw, we've now had two new entries in the top 5 since Trump took office, I don't think we're done setting records either, get your friends and neighbors to go to the next one
These rallies/protests/whatever are exactly how you build momentum for a general strike.
A general strike is useless without a significant percentage of the population joining. As these protests keep happening the attendees trust that the networks that are drawing them together will step with them into more drastic action, like a general strike. We are building a small amount of trust and cooperation between literally millions of people. It's not going to happen overnight.