A typical microcontroller like a Raspberry Pico ESP32, or Arduino has 520K of RAM. Not Megabytes but Kilobytes. There’s no OS. There are no drivers. There’s no sound or video output. You run a development environment on your pc, it compiles the code to byte code and then you transfer that data to the rom built into the microcontroller using the development environment because in most cases the Microcontroller flash isn’t visible to Windows/Mac/Linux as a fat drive.

Using a 1GB Pi as a microcontroller means you boot Linux, run Scratch/Python, C, type your code, and test it dynamically. You are running a single simple program that would otherwise run on a 200 Mhz CPU with 520k ram. So a 2.4Ghz Pi with 1 Gigabyte ram is gigantic in comparison making development much easier.