I'm really good at math so I knew that learning the algorithmic thinking wouldn't be hard. All I needed to do was learn to program and learn algorithms. For people with a different skillset it wouldn't be as easy, but reading about it online made me realize that it wouldn't be hard for me.

I mean, when you read about interviews and the problems people struggle with you get a sense of what it is. When I read those I thought "That doesn't seem hard, I can do that!", so I did.

What you are describing is exactly survivorship bias.