They decimated their DOS competitor which was capable of running windows 3.1 as well by specifically detecting if it was their competitor as the underlying system and throwing fake incompatibility errors and-well better read. https://en.wikipedia.org/wiki/AARD_code
But yes windows will, through incompetence, malice, or otherwise overwrite all other bootloaders whenever given the chance.
The AARD code was a segment of code in a beta release of Microsoft Windows 3.1 that would issue a cryptic error message when run on the DR DOS operating system rather than the Microsoft-affiliated MS-DOS or PC DOS. Microsoft inserted the code in an attempt to manipulate people into not using competing operating systems; it is an example of the c...