Maybe the NSA just wants to make Windows more secure, to make cyber-warfare harder for everyone else. But assuming the NSA is malicious, it wouldn't need to in

Maybe the NSA just wants to make Windows more secure, to make cyber-warfare harder for everyone else. But assuming the NSA is malicious, it wouldn't need to install a back door. "Helping" with development gives it access to the Windows source code. Thus it gets a better shot at finding vulnerabilities it could exploit. They just need to stay ahead of patches.