The pivotal explanation lies in Eren Kruger’s possession of the Attack Titan. This possession also grants him access to past and future user memories. Eren Yeager, the future Attack Titan wielder, is part of this lineage, allowing Kruger access to information transcending time.
How could Eren Kruger know about Mikasa and Armin?
During a conversation between Grisha Yeager and Eren Kruger, fans were left puzzled by how Kruger knew about Mikasa and Armin when they hadn’t been born at the time of the discussion.