Huh? They chose to fight back against the emperor, they didn't have to. The group made multiple choices along the way of who to ally with, where to spend limited resources. When to save innocents or raid the caravan bringing payment for the soldiers to fund their revolution. They uncovered secret plots and were betrayed when they didn't suspect an ally of being a spy despite multiple hints.
But at various points I gave them major arcs they could pursue. At the end of most sessions I tell them "here are the obvious options and opportunities in front of you what do you want to pursue next session or do you want to do something else?"
That's not a railroad, it's an open road. I create the map, they decide where to go. It's a far, far cry from saying "I don't want drow as a playable race" to saying I run a railroad campaign. But even if I did (which most modules seem to), who cares if everyone at the table is having fun?