1. Lack Of Proper Trading Education
2. No Risk Management
3. Lack Of Patience
4. Having that mindset that trading is an easy money generator.
5. They set up goals basing on others positive outcomes
6. Emotion
Lots of experience or things that you should face on first before for you to able to learn.
It will vary on each person because not all would have the same effort on learning things up.
If I may add also, sometimes when a trader experienced a huge loss, he will think that's the end of his trading career. Especially if the money that he used is not his but others who trusted him to make good in crypto trading.
In trading, you should be prepared to all possible circumstances that you will encounter especially in crypto, as the movement is very fast.