I think some of the reasons why lots of people tend to get scammed easily is because they are so trust-worthy and that they believe that this crypto-world can change their lives for the better. Another, is that they have no idea or lack of idea on the project they are involved with.
That's true! Specifically, all of that happen because people don't have knowledge and understanding about the market. They jump into the market without learning anything. Therefore, they can't know which is right which is wrong. That's why they easily got scammed by scammers. I always advice for newbies that they should spend time to learn before investing in anything!
I don't know how people become greedy and stupid at the same time. Many say here it's greed, but I agree with this lot saying it's ignorace and others saying about impatience. A greedy person might have lots of patience to be able to get his plan working. A greedy person might be very intelligent to come up with a plan to scam people. But a middle class bloke with money to invest might be impatient enough to enter to a deal and not study it and see if its scammy or fraudulent in nature, but he is not greedy for money, he just want to double his investment and was not able to get to the information that would save him his investment.