Theory number 01:
Remember the movie 300? The Spartans were happy that they were given an honorable death by fighting for their country side-by-side with their King.
This could be a possible reason why Solis gave up the fight. Perhaps he was looking for a graceful exit from the boxing industry and the only way for him to have an honorable exit was to fight with the champion. It was his first loss in the history of this career. This event offered him a graceful exit. What could be better that be defeated by the world’s champion right?
Theory number 02:
According to liguified , perhaps Solis idolizes Morales so much.
Theory number 03:
Please write it as your comment.