The idea that Messi moved to MLS because he was no longer capable of dominating at the highest level never really held up to scrutiny.
By the time he left Europe, he'd already won everything there was to win. The move looked more like a lifestyle choice than a footballing necessity. He chose a different environment, less pressure, and the opportunity to enjoy the latter stages of his career on his own terms.
Now he's back on the biggest stage, scoring a hat-trick in the opening game and once again looking like the most influential player in the tournament.
At some point, people have to stop searching for excuses and start appreciating what they're watching. Not every great performance is a conspiracy. Sometimes it's just the greatest player of his generation reminding everyone who he is.