Many of your points are management bullshit.

Yes, they are and I never said they weren’t management BS. Nevertheless management pays the bills, management makes the decision.

The key point is that they want a contract with a company so they can discard the responsability of failures on someone out of their own company.

You’re just saying what I said before…

The last problem is from Microsoft that worked hard these last years to remove any compatibility between office and other softwares of this kind

Yes, but the end result is that nobody sane would even risk not using MS Office and that’s what it is.

Large companies need an it service for Windows on top of the licences and infrastructure. It’s way cheaper with Linux.

It depends, integration between MS products and services usually comes out of the box or working with minimal setup while with open-source solutions / Linux that isn’t always the case. Also Windows sysadmins are usually cheaper because you can get more and they require less training to be “efficient” than Linux ones.

The biggest work with an enterprise Linux is to make it compatible with the shitty Windows environment, and the compliance with the useless security thought for windows.

Yes but you still have do it and it has a cost. Simply going full Windows is cheaper at that point.