Why did no great change in the society of Southern Spain occur in the years immediately after 1264?
The thing of greatest note in Spain in 1264 was the eradication of Muslim power in that country:
In Spain, King James I of Aragon reconquers the cities of Orihuela in Alicante and Elx in Valencia from the Moors, ending over 500 years of Islamic rule.
It would appear that with the fall of the Muslim empire in places overthrown by the Spanish, treaties between the two maintained peace for the next two hundred years.
The taking of these areas ended in 1246, but did not begin then or anytime in the recent past. What is known as the Reconquista took place over the course of 700 years. It was a long time of upheaval in the Middle Ages. The goal of the "Christian kingdoms of the Iberian Peninsula" was to take possession again of lands ruled at that time by the Muslims in the Al-Andalus Province. In this onslaught of the Spanish (the Christians) against the Muslims, there were three locations targeted:
...the Castilians in central Spain, the Aragonese in Catalonia and Valencia in the east, and the Portuguese in the west.
First, Muslims were conquered in 1212 at the Battle of Las Navas de Tolosa. Strategically, this delivered control of the entirety of central Spain into the hands of the "Latin kingdoms." Cordoba and Seville had long been primary Muslim strongholds, but they fell in 1236 and 1249 respectively. In 1246, Ferdinand III of Castile executed the Treaty of Jaen with the Nasrid ruler of Granada. There would be not resumption of war against the Muslims for the next two hundred years (at which time Gibraltar would fall in 1462).
With the marriage of Ferdinand and Isabella, a mighty alliance was formed between the kingdoms of Spain, Castile and Aragon. It was impossible for the Muslims to regain what they had lost in the face of such a strong alliance. Because of the expulsion of the Muslims and the treaties established, peace remained for many years— whereas for many years prior, the Spanish had been fighting to drive the Muslims (non-Christians) out of Spanish lands that the Spanish had previously lost to them. I believe this is why there were no great changes immediately after, as these Spanish kingdoms would have been interested in rebuilding the treasury and military, etc., during peace time. (This was the case after the Tudors took the throne in England after the Wars of the Roses. It would be many years before the Renaissance would take place and great changes would take place in England, as the rulers of the Tudor dynasty worked to bring themselves restored peace and power. Elizabeth I, Henry VIII's daughter, would ultimately refurbish the treasury, establish England's military power, and usher in the period known as the Elizabethan era or the English Renaissance.)