maybe the same reason why they get involved with a whole lot of other shady stuff, the greed!
it actually seems to be a strong driving force in the cryptocurrency market. people even buy bitcoin out of  greed, they want to get rich overnight, and don't get me started on altcoins and their pump and dumps.
so the same thing is true about  bitconnect and all the similar projects. people get involved with them because they think they can make money, they sometimes even close their eyes on facts because all they see is money!