1000 Bitcoins, in what period of time? This is enormous amount and would be very, very hard to get. Unless if the person is the criminal so it can use other means and criminal activities to get to the coins. But with no trading or Bitcoin connected job you can earn that much in your lifetime. Unless you are Trump. 
Or unless you have the knowledge that's required for a high paying job. 1000BTC is not that large if you look at the top of the chain. Of course not all of us are a candidate to such job but you get my point. It doesn't require to be illegal or some shady business, you just have to know something that others don't or have a skill that others can't do. Actually, even committing crime to get this amount of money will require a good amount of skill and knowledge.
For example, the famous ICO scam. They can't do it without knowing how to make a coin, start a team, and how to exit the scene without leaving a trail. 1000BTC is far from the amount of money that you can get from mediocre crime. You have to do something big to earn this much from a shady business.
