Yeah they did

Tldr: When diplomacy failed then the rebellion went from small isolated cells to a large unified force.

There were still rebel cells doing their thing but they didn't really have a huge amount of support broadly until the empire started really cracking down on even the slightest of slights against them (like literally cracking down on people openly criticizing the empire).

Then the rebellion starting entering the mainstream as something that was taking place and the rebel cells started getting a lot of support.