Buddy, given your relatively basic questions and how you're posting to every single fucking vaguely relared community, I would highly suggest you do some studying on just... basic computer concepts and how to use them. Not sure what resources are out there anymore, but maybe some basic "these are the parts of a computer, these are programs and how they work" stuff from the 90s. They used to do middle school classes on how to properly use google and other seaech engines to find trustworthy information for citing in research papers. I seriously suggest you start there.

Then, after you understand the basics maybe you start trying to understand how all of that works in regards to security and the concept of trust in the software you install and run.

Spoiler alert: Computers are not designed with any sort of "zero trust" architecture like you seem to be shocked that they don't have. Things are not sandboxed, segmented, or otherwise prevented from accessing other stuff as a general rule.

This is why one of the bare minimum basics is "don't run anything you don't trust".