Why do some scenarios start with just a few people?

[Xalon]

I had a Scenario pop today and there were 2 Destro and 5 Order.

1 - how does this happen?

2 - when it does happen, is there a way to end the Scenario?
(someone did this but I didn't get a chance to ask them how)

Would be great to have some scenarios with less players, even if is 3v3 or 6v6. But once it starts and you are outnumbered by 2 to 1 or 3 to 1, there is no real way to continue lol