Celebrities whose deaths were overshadowed?
I would say the most famous example is Farah Fawcett. There was huge outpouring and then a couple of hours later, we learned that Michael Jackson died which totally ecclipsed FF's death. At least with Farah Fawcett, she was battling an illness so it was kinda expected. With MJ, that came as a total surprise especially since he was planned to do the whole London comeback tour thing.
I felt bad for Farah though. To die on the same day as MJ, you will always be overshadowed. I think MJ was literally the most famous person in the world at that time.