It is worth noting that a functional operating system can fit in ~16MB. Tiny Core Linux is a real, legitimate Linux distribution that boots to a command line or basic GUI in under 20MB. However, it:
October 26, 2023 Subject: Feasibility and Security Risk Assessment of Ultra-Compressed Windows 10 Images
Decompressing an 18MB file into a 4GB functional image requires immense CPU power. On an average laptop, this "quick download" could take 5 to 10 hours to extract, often failing at 99%. 3. System Instability