A bit on the oversimplistic side. Don't know if it's due to space limitations bu definitely it suffers of reductionism.
First, remences (pl. for remença) were those pagesos (the Catalan pagés/os translates as peasant/s) affected by a remença contract, but they were a minority of the pagesos. Moreover, not all the remences revolted against the government of the Generalitat (which still acts as the Catalan legitimate government, even if it's now limited by the Spanish one).
Second, the urban classes were also split in both sides, as not all artisans welcomed the king nor all buscaires looked at him as more than another greedy lord; Joan II passed into history as Joan "Sense Fe" (John the Faithless) and, while looked upon as a consumate politician, is considered a ruthless, egotistical and cruel despot, not one bit of an injustice conscious defender of the feeble or anything like that.
Third, the nobility was split between the royalist and the Generalitat sides. Actually it was a war of the king against the Catalan government; the Biga/Busca confrontation happened along the way, before and after such a war. The king cared not a dime about the peasants or the artisans but for absolute power for himself, and the much autonome character of Catalan institutions went frontally against such an intention. Take into account that the Counts of Barcelona had to pay due respect to an oath that put their sovereignty over Catalonia at the same level as the rights of their subjects; even after becoming kings of Aragon, the Counts had to take this oath to be able to rule Catalonia as well.
King Alfons ruled from afar, as he loved his Italian domains, but such a ruling was frowned upon in Catalonia, where it was an ancient understanding (the Casal, or House, of Barcelona dated back to the 9th century) that the sovereign of Catalonia must stay in Catalonia as muh as possible, to be in contact with the subject people and lands. He also wanted financial support for his campaigns in Italy.
Alfons is considerated as a great figure, but really he behaved like those "great" kings whose extraordinary acts rely on overtaxing and exhausting thier very subjects, firmly rooting contempt and dissent and laying the foundation for civil war and/or decline.
The conflict grew in the first half of the 15th century as the kings demanded money for their own "patrimonial" wars and the tension between the growing urban midle class and the minoritarian but active remences and their landlords did not decrease but in very small degrees. Also remences were organised, as other peasants, having their own syndicates, assemblies etc.
When the civil war (1461-1472) erupted, the Generalitat had evolved a compromise that largely satisfied the remences' demands (not equalled until 25 years later when the problem was finally fixed), but the most militant remença minority rejected it. One cannot help but link such an attittude to the interests of a select few in the royalist camp; the remença leader got a nobiliary title after the war as a prize from the king, such an irony.
The church was also divided, it's plain not true that it fought the king; in fact a bishop from Girona played heavily for the king. It became a matter of land holding and particular interests: both clerics/churches and nobles in both sides held lands and peasants, and fought the other side for benefits, even the case being that families had siblings fighting in both sides to play safe with their riches and patrimony. After the war, nobles who fought for the king got the spoils and added lands and riches from defeated nobles to theirs, the peasants' situation not getting well by a bit. That's why remences revolted again, led by a subordinate civil war commander, in the 80s, only to be defeated and repressed again, until their problem was fixed later.
Finally, it was a civil war of sorts that really devastated the land, but lots of foreginers fought in both sides. The Catalan government gave the crown to a Castilian, then a Portuguese, then a French candidate when the formers died or renounced, and many French, Portuguese and others fought in both sides. It also had its up and downs, and the royalist side was in the verge of losing at least two times, first when the Generalitat troops unsuccessfully besieged Girona in 1461 where the queen and prince hid (a tunnel incursion was discovered when the first troops were entering the citadel), then many years later when prince Ferdinand was almost caught at the Battle of Viladamat.
Just an interesting bt more. The Admiral of Catalonia (commander of the Catalan navy, one of the most powerful in the Mediterrnean) for the Generalitat was a Joan Colom, expert ship captain, who was also brother to a chief of the Taula de Canvi, a Catalan central bank of sorts in Barcelona. He exiled after the war and is said to have sailed for the Danish before returning home to bid for money to finance a journey to the Indies using a west route. Yes. Colom=Columbus.
has been spending time in paradise lately.