Our galaxy has 200 to 400 billion stars in it so no matter how low the odds, there must be life out there somewhere and if there isn't any race that has faster than light travel (needed to reach us), could probably travel between different galaxies. Very big numbers make even miniscule odds possible. Its harder to prove that life doesn't exist in the galaxy, universe whatever than that it could exist.
I'm sure radio broadcasts predate Hitler by about 20-30 years.