I'll ignore formal education, because it's obvious how that works. I never got a college degree, just high school. I've learned everything else by doing.
I suppose it's about being curious, and falling into rabbit holes. Expanding knowledge for the sake of knowing more. Learning something new is so much easier with the internet. I'm old, and pre-internet, learning something new meant buying books, or going to the library, or learning from someone else directly. I learned MS-DOS from a thick book I bought.
If you only know the goal, you just need to search "How do I...". How do I make pizza or bread. How do I learn linux. How do I repair a fan. How does GPS work. How do bees navigate. Also, when you run across words you don't know, don't just skip over them, search the word, it's right there in front of you. My dad taught me this. He told me to read with a dictionary next to me, so I could look up words I didn't know. I still do that now.
Generally, I just dive in, and learn as I go. But, I also pick up knowledge of anything that interests me with no current need for it. I've learned a LOT about how houses are built from watching Perkins Brothers on YT. I'll probably never build a house, but I know in detail how it's done now. From that show, and other sources, I learned how important planning is. There's a point in the planning process where you just need to start actually building it. Money is the main driver, and people tend to do the bare minimum of planning so they can get started. That causes problems throughout the build.
Planning is the start, and it's relatively cheap. The further along the process you get to the final goal, the more expensive mistakes and changes are. If you're doing the job for a client, the most expensive mistake is the one the client catches at the end of the project, that you missed. Because, they lose trust in you.
As an example of learning, I recently refurbished a desk. I've known about applying laminates with contact cement generally for many years, I came across the technique and read about it out of curiosity, but never had a use for it. Actually, I first learned about contact cement when I was a teenager, and build a kayak out of plywood and canvas. Before I did the desk, I watched several videos and then bought exactly what I needed for the task and gave it a shot.
Several years ago, I dove into learning Blender. I did that because I needed/wanted it for a work project when I was a graphic designer. Previously, I had been using sketchup but I wanted something more robust. I followed some tutorials, then applied what I'd learned to my project, searching for solutions to specific issues as they arose. I enjoyed it, so I started using it for personal projects. If I hadn't enjoyed it, I would have only learned exactly what I needed to, and then left it. I know Blender pretty well now, at least the modeling and rendering parts.
Here's a table I designed in blender that I'll be building soon.
I've used blender to design houses in great detail that will never get built. I did it for fun.
A new product idea popped into my head, a "better mouse trap". I had the money, so I bought a 3D printer, assembled it, and used Blender to model the parts and made nearly-complete working prototypes. I've left the idea to rot, it hasn't gone anywhere yet, but I have a 3D printer, and I know how to use it now.