Real is teh most successfull cuz
Franco put large amounts of state reserves into Real Madrid, as the name means "Royal Madrid" strangeley enough, in order to allow them to be better than any other side, particularly Barca who, as a Catalan club, did not want to be part of Franco's regime and were in direct opposition to everything he stood for. When Franco’s fascist forces finally prevailed over the Republicans in 1939, Barça, who had narrowly survived the Civil War, came in for a pounding.
Real Madrid - Franco’s team - was to be deified. Officially.
State-controlled Spanish television continually showed highlights of Real’s matches and very little of Barça’s, thus generating the notion among the populace that Real were Spain’s team, whilst also allowing Real to take a far larger share of revenue.
A Franco stooge Barça president managed to ‘lose’ Alfredo Di Stefano to their arch rivals when they’d already signed him. Di Stefano went on to lead Real to five successive European Cup victories.
The Spanish referees were also got at in a regime of terror. Not only did they favour Real in any encounter with Barça, the 1940s, 50s, 60s and 70s were also littered with bizarre - and obviously biased - refereeing decisions in other matches involving Barça which cost them championships and Cups. The decisions were so appalling that eventually even a puppet Barça president had the temerity to complain to the Spanish College of Referees. He was ignored
