Many government orgs have spent the last decade and a half slowly transitioning old legacy applications and platforms to browser-based alternatives. That old ERP software that used to require a thick client? Now it runs in Chrome. Microsoft recognized this and smartly moved to keep these customers locked in via an ever growing Microsoft Office bundle - subscription based, with Teams for their chat and then building up additional capabilities to extend the dependency, like InTune.

Where we are at now is that the pain of moving away from Windows is acceptable for many larger organizations and governments, especially those with flat or decreasing budgets. You can just swap out the OS layer and keep other processes the same - keep using Office with just the browser versions if you want, or move to an alternative (like EU-based). Teams works on Linux. There is no moat on Windows anymore