Was something going on in the Baltics during the 1900s that would cause Baltic Germans to hide their identity?

My great grandfather and his wife, my great grandmother, seemed rather keen on hiding their Baltic German ancestry through name changes and obvious lies about their ancestry. They instead opted for a more all Lithuanian ancestry. My great grandfather was born in 1889 and my great grandmother was born in 1914. My question is was there anything going on at the time in the Baltics that would cause them to feel the need to change their identity?