I do too *cries in hands* William left because he wanted to pursuit the theater, which is his passion. I hope and pray that he returns to CSI, because I hate theater, no offense to him of course.
The show is going downhill (at least for me) and in some seasons lots of 팬 will feel that way and start abandon the show. The producers of course don't want to see that happening so they will bring back Grissom and all the old 팬 will come back running immediately.