You have to read the book, "Catalyst." All is explained there. It tells the story of Galen and Krennic's struggle to complete the Death Star Project.
Lyra Erso confronted Krennic because she knew what he was doing. She saw through his lies and deception masking the Project. Krennic attempted multiple times to recruit Galen throughout his career, and when Galen was working on the project, freak accidents occured, resulting in mass casualties. Lyra didn't want Galen a part of it, but Krennic distracted her with vacation trips sometimes. In the end, she saw this as her last chance to stop Krennic from taking her husband. She knew Jyn would be safe with Saw.
As for the Geonosians, the entire population was killed off. Krennic had negotiated with Poggle the Lesser and his caste to work on the project, but when Poggle rebelled and the Geonosians destroyed their 3 years worth of work, Geonosis' population was wiped from the galaxy. No one survived.
"Catalyst" by James Luceno is the prequel to Rogue One. Read it, highly recommend it!