Space

Occam's Razor is not a proof, it's a way to prioritize resources onto more likely hypotheses.

last 100 years of radio until we die as a race.

Based on our own experience, over the last 100 years, radio signals have gone from very scarce, to a cacophony of millions of high bandwidth compressed and encrypted emissions that look like random noise from anywhere outside our solar system.

If we consider an intelligence with an evolution similar to our own, "in the clear" transmissions that might've reached Earth 200 years ago, would've gone completely unnoticed, while now we could be getting the sum of their thousands of Tbps of encrypted memes, and be none the wiser.