It's really difficult to judge the squads back then in comparison to today, everything I know about that time is from what you can read, what my father told me and the few videos you can watch. From what I know, quality players stayed longer at their own club, often never moved. You rarely had teams like today, full of international superstars. So even at the big clubs often enough only a few players were brought in and the rest needed to make it work. You also rarely had a lot of squad depth. Let's not forget that substitutions weren't allowed until the late 60's if I remember correctly. So quality players stayed at their clubs and only with great nationalteams we saw teams full of superstars. That means that the difference in quality between top clubs and small clubs wasn't as big as it is today, at least that's my opinion (and it's no surprise that records of points totals were broken in most top leagues in the last 10 years). But it was a bit easier to stand out between the top teams and if one team got it right (often because of a great youth generation) they were superior to the other top teams for a while and it showed in the competitions. So I'd say it was more competitive between the top tier and the rest but less inbetween that top tier. That's also why the top tier often changed until the 80's when money became more important and certain big clubs established themselves because of it.
So I'd say it was obviously easier for di Stefano to turn Real into that superteam than it would be for Ronaldo (or anyone else) today, I actually think it's impossible today. You probably can't have that big an impact as a single player at a top club. But that shouldn't take anything away from what he did and achieved. Probably that's also why Maradona really failed to turn Barca into a truely great team (he really was a whiny annoying bitch in his 2 years there) but was brilliant in turning mediocre sides into title challengers. In a team full of superstars you rarely get away with that one 'I want to do it all' player, who outshines everyone else.
Can't really comment on the politics back then, but as far as I know politics and also the status of superstars were always highly influential at Spanish clubs. Pretty sure jojojo knows more about all of that than I do.