[If] OP is interested to make giveaway than send each person to 1 key than we have chance to get some balance.
Duh. The point is they're not doing a giveaway. They're doing a stress test (AKA DDOS).
We're not doing anything.
You are using the power of human selfish greed to create a DDOS on the network. It's actually a pretty smart idea for creating a stress test.
I myself tried building a couple raw transactions, but with the amount of dust inputs it's a ton of work just to make a raw transaction of just 0.00005. Not worth it.