Long story short. I think it was when this image was built in my mind. Someone who seemed very technically skilled said to me, you have to exercise that knowledge or those skills otherwise you forget stuff. So, I keep reading and using Linux over and over, it's not necessarily a Eureka moment for me.

Before that I had many occasions when I couldn't run simple commands. I had to read and re-read about git, terms like PATH and The POSIX standard, But then I found Bitcoin gave me a direction to learning Linux and when the penny dropped, it was an awareness to Linux, Bitcoin, and how all the packages and libraries in between them work together.