Remember that time that Jon Snow died and was brought back to life by R’hllor to fulfil an ancient prophecy that could very well be humanity’s last hope?
King Viserys tells Princess Rhaenyra of the prophecy, which is treated as an ancient Targaryen heritage. In his words, Aegon the Conqueror foresaw the end of humanity.
Jon Snow’s royal status also aligns with the Prince that was Promised prophecy. He was, after all, a prince, and when he defeated death with the blessing of the Lord of Light, he proved that he could have been the Azor Ahai that was foretold by the Red Priestesses.
The Prince that was Promised has always been a pivotal character in many myths in Westeros, and Jon Snow seems more than likely to be the one chosen by the prophecy (especially in King Viserys’ last words).