Many of us have seen scams so ridiculous that surely no one could fall for it right? Things like "your late great Uncle has left you a fortune", or "you're a winner in the International Lottery". Why are some scams like this? Surely they wouldn't succeed?
Basically when cyber-criminals are trying to trick people, they will go for one of two outcomes:
1) Make it realistic, and trick a small percentage of people
Here they're not actually going to do much work - they sit back and hope a small percentage of people will be tricked into following a link to a malicious website, or a fake website. From here, maybe that website can hack your computer, or trick you into providing confidential information like your bank login details. So in this case, the scam needs to look believable, because they want as many people to click as possible!
2) Make it obviously fake, and talk to a very small number of people
Some scams require the personal touch though. e.g. They'll be corresponding with you. In this case, they only want to talk to the most gullible of people, and unfortunately there are still people who fall for these scams. If someone truly believes that their long lost relative found $20 million of Gold in the Iraq war, then that's the person they want to speak to, because they're more likely to send money to deal with costs associated with splitting up the treasure! They do not want to speak to people who believe it's a scam, because they'll only be wasting their time.
So don't be gullible. If it's too good to be true, it probably isn't true.