#4. 2 cases of superstars refusing to perform were for religious/political reasons
As you probably might know, Sami Zayn is a Syrian Muslim. Due to the religious conflicts of the region and Saudi Arabia's hostile relations with Syria, Sami Zayn likely would have had to worry about his life if he went to Saudi Arabia.
It's similar to the case of Armenian football/soccer player Henrikh Mkhitaryan. He plays for Arsenal Football club, who will be travelling to Baku, Azerbaijan for a major European tournament final. Being an Armenian player, he was made to miss the final despite being a key player, primarily due to the hostility between Azerbaijan and Armenia and his own personal safety.
As for religious reasons, Aleister Black is a known Satanist, the first in WWE. While that doesn't really make a difference anywhere else, he likely has to worry about his life in a country which is known to be extremely religious in the most rigid way possible.