For example, they choosed school principals among independentist so now over 85% of them are Catalan language teachers that tend to be independentist. This way kids could be directed to be independentist too.
The same happened with the local media, TV3, newspapers like La Vanguardia. If you were not independent public funds were not given to you. Those private media without the public funding could not live on their own.
Since 20 years ago they control education too, and kids are forced to speak Catalan as the main language, studing a very biased History full of lies like that Catalunuya was a reign in the past. They also put big sanctions on shops labeling things on Spanish until nobody dare.
They brought nearly a million muslim people to Catalunya to work so they do not speak Spanish, like people from Spain or South America does. This makes it the higher terrorist risk area in all Spain, including Ceuta and Melilla.
The problem was not independentist forces doing this, but the central gobertment that let this happen.
Now with half the population(controlling Catalunya) against the other (supported by the Govertment) there is a significant risk of civil war there.