Despite your best efforts sometimes you simply cannot follow. Maybe you have a values conflict with the leader, the organization, or the cause.
There could also be a vacuum. No one is leading an effort. That’s when it becomes your calling, and you step up.
You won’t necessarily be cheered or supported, and it won’t be easy; but that’s not why you lead, if it is, move over to make room for others aside.
Others have said it many times before. You always have options. If you can’t follow, lead. If you can’t lead, step aside.