I don't remember the exact numbers but in 2013 I bought some tesla calls planning to sell them in a few weeks and hopefully make a few bucks. I forgot to sell

I don't remember the exact numbers but in 2013 I bought some tesla calls planning to sell them in a few weeks and hopefully make a few bucks. I forgot to sell them and when the contract expired they were in the money (TSLA had gone up almost 300%). Etrade bought the shares on margin on my behalf, and when I next logged into my account I was first shocked to see I owed Etrade about $16,000 and then amazed to see that I owned about $50k worth of tesla shares (on a maybe $1000 investment, I don't remember what the premiums were at the time). So the short answer to your question is, dumb luck and sheer stupidity.