From TROS novelization:
Thanks to some risky assignments led by Poe, Rey, Finn, and Snap, they’d learned that the First Order had been doggedly perusing their sympathizers, restricting communications, cutting off supply lines, capturing or even assassinating allies. In short, no one had answered the call because very few had even heard it.
Makes me feel sick lmao. It’s probably the biggest retcon I’ve ever heard. The others in this movie I consider clarifications bordering on retcon, but this one is absolutely a retcon.