Bands where a member leaves, and BOTH that member and the band become more successful as a result

Okkervil River and Shearwater are an interesting case. Shearwater was originally an Okkervil River side project for songs which didn't fit on their albums, and for which writing credits were more or less split between Will Sheff and Jonathan Meiburg. I think Meiburg became dissatisfied with this arrangement so he left OR and after that SW became more or less a Meiburg solo project. Since then Shearwater have become much more successful than they were before the split, although it's a moot point whether OR have also become more successful.