For me, it was the realization that some languages have REPLs and can be used just like bash. Since I started with Linux sysadmin and worked my way into programming, I found a lot of the details of programming hard to understand, e.g. runtimes, compilation, dependencies. Most intro compsci classes I've seen tend to use C++ for some reason.

But, once I started using Python, and specifically the ipython interpreter, I realized that programming didn't always have to be statically typed and compiled and work with a Makefile. It could work like a bash prompt!

Eventually, I did branch out into Rust for compiled languages, but my REPL realization gave me the ability to experiment and "fail fast" in a more familiar environment.