Yeah like crypto or not, why would you be paid instantly for doing nothing ? $3k is a month or more of work for most people, did that person really believe the world lied to him and instead of working a month, he could "double" it immediately ?
They probably did. It's because they've heard of other people getting rich off of crypto. The classic get rich quick swindle. Ponzi schemes and all sorts of other marketing schemes are also similar.
Seems insane, but it's essentially no different from any other kind of gambling. Suspecting that the game is fixed doesn't stop a lot of people from betting the house regardless.
