The key to understanding this Attack on Titan mystery is that baby Eren did not actually possess the power to see the future. If you're referring to the scene at the end of the anime where Eren appears as a baby while the future Eren's words about freedom play in the background, the series is connecting Eren's childhood to the future he eventually creates. It's a powerful visual, but it isn't proof that Eren had Titan powers as an infant. The actual explanation comes from the manga and anime's treatment of Paths and the Attack Titan's ability to transmit memories across time. The Attack Titan can access memories from future inheritors, as revealed when Eren Kruger tells Grisha to protect Mikasa and Armin—two people who had not even been born yet. Later, after kissing Historia's hand, Eren sees memories of the future through Grisha's memories. When Eren eventually gains access to the Founding Titan's power through contact with Zeke, his connection to Paths allows him to influence events in the past. So, if you're referring to the baby Eren scene in the finale, it is best understood as a symbolic or Paths-related visual, not a literal instance of infant Eren seeing the future with his own mind. The series never establishes that baby Eren had Titan powers or conscious future memories at that age. The scene connects the innocent child Eren was to the adult Eren whose choices shaped the future, reinforcing one of the story's central tragedies: the boy who longed for freedom eventually became responsible for unimaginable destruction.