Questions about Spiders Vs. Scorpions

So, I have a few questions about the event.

I understand it's a large event, but I feel like the ranking is terrible. I mean, I join a room or go to the lobby and see many people - much more than only 10 - with the crown next to their banner. Also, what the hell is the deal with the rewards? Are they distributed after each round or after the entire event? If it's after the entire event, are your rewards based off of how well you did that round or how well you did the entire game? Does anyone have any information clarifying any of this?