On the other hand, DES is an example of where people were sure that NSA persuaded IBM to weaken it but, to quote Bruce Schneier, "It took the academic community two decades to figure out that the NSA 'tweaks' actually improved the security of DES". <https://www.cnet.com/news/privacy/saluting-the-data-encrypti...>
NSA did persuade them to weaken DES by shortening the key size. The "magic S-boxes" were chosen to be resistant to differential cryptanalysis (which was successfully kept secret for decades to come) but that doesn't change the fact NSA had the means to break DES by brute force.