In recent episodes, it was brung to our attention that corrupted gems were infact corrupted by the Diamond Authority. It is also confirmed that the light we saw at the end of Lapis's story in the episode "Same Old Word." When Centipeedle was telling her story to Steven, we find out that it was not only a light but a song as well. It could have been some kind of light as well. Is it possible that the Diamond Authority sung their corruption song and magnified it across Earth, therefore corrupting all the living gems on Earth. This of course excludes the close friends Rose was able to save with her shield. I believe there is more evidence behind the Corruption Song being a real thing. The woman that voices Yellow Diamond is Patti LuPone. She is an actor and SINGER and is BEST-known for her stage MUSICALS. Hiring her was no doubt costly and why would Rebecca and the Crewniverse pay so much for such an amazing singer and not have her sing. I believe that Yellow Diamond alone or maybe all the Diamonds sing a song that causes gem corruption. I believe we will hear this song in the future as a second attempt to corrupt all the gems on Earth, this time Steven being the savior. Also, just to be clear, I suspect it is not the actual lyrics of the song that cause corruption but the voice making Yellow Diamond's voice her weapon.
This is just my opinion and please reply with what you think. :D Thank You!