It is for sure to get trust from the early investors to encourage them to invest more. And after getting lots of those second investment from people like you they will run away in a blink of your eye. Try to be away from these ponzis.
Yep, this is an age old scam. And I'm amazed people keep falling for it. But I guess that's why it's been repeated so many times as there is an endless amount of suckers apparently.
Simple method, payout in the beginning to lure people in; then when you have the right amount of money turn and run for the hills. Stop falling for the nonsense people and there won't be so many of these kind of sites around.