Complex sentence: This development was slowed by the German electronic's industry's decision to stop researching microwaves shortly before "Rotterdam Gerät" literally fell from the sky, and a lack of suitable crystal detectors that were key to the British receiver designs.
Split into simpler sentences: This development was slowed by the German electronic's industry's decision to stop researching microwaves shortly before "Rotterdam Gerät" literally fell from the sky. Another serious problem was a lack of suitable crystal detectors that were key to the British receiver designs.