Well Messi is probobly full of playing football and just wants to have fun a little and earn a lot more money in the last years of his football career. After he won the world cup he dosent have to win anything so there isnt anymore motivation for him to play at the top quality level as before.
Today, football players can continue to play football until their very old age. One of the best examples of this is Ibrahimovic. Even if Messi does not play football until the age of 42, he can play professionally for a few more years. For this reason, it is a very correct decision to choose to spend his last years in an easier league. I thought he made the right decision when he moved from the Spanish league to the French league. Now he will most likely go from the French league to the American league. I think we can say that he made the right decision again.
The money factor was not the most important thing, he had been planning it for years, anyway, the most important in his transfer is the possibility of playing in some of the South American club interleagues.
There is no such thing, but he shows that money is not everything and his transfer can be a rule changer between those two confederations.