what would happen if Putin and Musk disagree at some point

Nothing significant. Musk is running on a purely American strain of right-wing revanchism. Trying to deflect all our problems onto Evil Foreign Man is a big part of why the country is as fucked as it is today. We simply cannot let ourselves believe that the fascist strain gripping our country by the taint is American born and bred. So every four years, Republicans accuse the Democrats of being Chinese and Democrats accuse the Republicans of being Russian, and then the parties do old fashioned American Protestant Capitalism to the country while we all writhe in torment, looking for someone else to blame.