Folklore related eading question

Boxing is popular in many countries. Two fighters wear boxing gloves on their hands. The boxers hit each other until one is knocked out or until the final bell rings. Each part of the fight if three minutes long. It is call around. Thai boxing is different.

The boxing match begins with music. Then the two fighters kneel and pray to God. Next, they do a slow dance that copies the movements of Thai boxing. During this dance, each fighter tries to slow the other that he is best.

Then the fight begins. In Thai boxing, the fighters can kick with their feet and hit each other with their elbows and knees. Of course, they hit with their hands too. Each round is three minutes long. Then the boxers have a two-minute rest. Most boxers can fight only five rounds because this kind of fighting is very difficult.

Thai boxing began over 500 years ago. If a soldier lost his weapons in a battle, he needed to fight with just his body. The soldiers learned how to use all the parts of their bodies. In 1560, the Burmese army captured Naresuen, the King of Thailand, in a war. King Naresuen was a very good boxer. He won his freedom from Burma by defeating all the best Burmese fighters. When he returned to Thailand, his people were very proud of him. Thai boxing became a popular sport.

According to the passage, Thai boxing became a popular sport -----.

1) since king Naresuen won his freedom from Burma

2) after the king of Thailand defeated all Burmese fighters and returned to his country.

To me, #1 is right. The passage says "he defeated ALL the BEST fighters", but options #2 is generalizing and saying "all Burmese fighters"; that's imprecise. However, answer key went for #2.

The only justification that crosses my mind is that the writer probably thinks that when we speak of great battles and feats of strength, especially in folklore, we don't really talk about those who didn't matter (the fighters which weren't the best). We don't care about that. That's the point of folklore and legends. What do you think? (We have this kind of Reading Comprehension Question in some old ESL exams, though.)