Why? Everything because of that russian plane?
What problem have russian Clubs because of that?
There are two moments here. Firstly, sport is always very political. There are several powerful hawks behind Russian Volleyball Fed, which by the way explains how Russia manages to maintain a high profile in volleyball without any public interest. That is, the "No" order is non-negotiable here.
Secondly, the problem is not the plane per se. Accidents happen, it is normal. The issue is that the plane was taken down deliberately, and this requires a response. The "lite" version of that is making lots of fuss and cutting the public/business relationships. The "full" version is a military response. Now, the bizarre about Nato and the fifth article is that the only cost-effective military response is the one that does instant incapacitating damage to the Nato-member vis-a-vis. That is, if Russia instantly takes Turkey out of the equation, then we get something like "we're super-annoyed...but isn't it Erdogan's fault?" Do I need to tell you that this scenario assumes certain health risks for the people who would be unfortunate enough to visit say Istanbul on that historical day?