I hate to say it, but everything is predetermined.
Imagine entering a black hole or wormhole. You experience time differently, aging much more slowly than everyone else. Eventually, you emerge somewhere far into the future, perhaps closer to the edge of the expanding universe.
From that distant location, the light reaching you from Earth is actually light from the past. Although you’ve traveled into the future, you’re looking backward in time, observing events that have already happened.
Now imagine repeating this journey, traveling back and forth through space and time. From one perspective, events are still unfolding. From another, those same events have already occurred.
Follow this idea to its logical conclusion, and you begin to see why everything might be predetermined. The past, present, and future are parts of a reality that already exists.