In the interests of a section of that state, though not others. Even in American politics there are competing interests. It wasn't in America's interest to let them nationalized, by ANY measure. Again we took all the equipment out, we took our ball and went home. However it was in the interests of FDR not to invade or coup Mexico, either because it would be too damaging to his pitch to the American people who had grown sick of interventions, or because they didn't have the means to do so. Or both, again Calles had become a US asset and him losing all his influence meant they lost all their influence. It had to be rebuilt.

Ugh I was gonna send you a link to a fantastic book on archive.org that I found super useful on the topic, but it is currently not borrowable anymore https://archive.org/details/empirerevolution0000hart

The book on the construction of the CIA and those links in Mexico post WW2 is still available, It is not Cardenas focused obviously, but paints a picture of what had to be grown in Mexico for the influence the US would have starting in the 1960s. https://archive.org/details/ourmaninmexicowi0000morl The empire is not all powerful and at times it must tactically retreat