my opinion is that NBK had to go because he is strong minded, not because he played poorly. I think the decision was kinda made more because of things outside the game and leading issues. My guess is, the goal was to give ALEX more control and aslong NBK was around, it would have created constant tension. so it was either him or ALEX. but that's my guess. no one knows, from the outside.
and yes, NBK is solid Tier1 and a legend. But French CS is and always has been troubled in some way. CSGO is a very emotional esport game. Keeping healthy realtionsships for years seems almost impossible to me. so much drama going on even though they all are professionals. but then again, only human, afterall.