This move, which seems trivial, is actually a little surprising. In most games in this line the knight is developed to d2, from where it can go to b3, c4 or f1. Caruana has another plan in mind.
1. e2e4  1... e7e5  2. g1f3  2... b8c6  3. f1b5  3... g8f6  4. d2d3  4... f8c5  5. b5c6 Caruana is an expert in this variation. The resulting positions are often simple in appearance and complex in essence, with many strategic details. 5... d7c6  6. h2h3 6.Nbd2 and 6.0-0 are more common, but Caruana has played this move already in 2023. 6... f6d7 