While working at office almost all best developers I know were working on the side job at the same time.

It is not about being in the office or working remote. It is about working with smart people.

Many devs I saw using their tablet or phone connect with their bluetooth keyboard switching between their office and remote project via tablet.

Mostly the slowest part of information work are not developers, project managers, managers, or others. Focus should be somewhere else.

But for me, it is funny to see business owner or managers trying to beat engineers who are working on maths and science since age 14. Almost all the salaries I am offered and worked for were nuts compared to what I earn from side project.