This number just isn't true, and let's try to put this idea to rest.
Let's use the CIA World Factbook as a source regarding religious numbers in Russia. According to a 2006 estimate, we have the following figures:
Russian Orthodox: 15-20%
Other Christian: 2%
The "Other Christian" are most likely evangelicals or heretical groups like the Jehovah's Witnesses and Mormons. So, when you hear someone say "1% of Russians are Christians," what they're really saying are "1% of Russians are Evangelicals." Even if this were the case, and even if one wanted to argue that these "Other Christian" groups are true Christians, the fact remains that it is untrue that 99% of Russians are atheistic. According to these figures, at least 35% of Russians practice some form of religion outside non-Eastern Orthodox Christianity.
Some might say here, "Yeah, but do those Russian Orthodox and Muslims practice their faith?" I'm so glad you asked - the CIA is even kind enough to clarify what these percentages mean:
Note: Estimates are of practicing worshipers; Russia has large populations of non-practicing believers and non-believers, a legacy of over seven decades of Soviet ruleSo yes, it's true that Russia has non-practicing believers (ie., false believers for whatever religious faith) and non-believers, and this was the result of the Soviet rule, however the numbers given by the World Factbook account for those actually practicing their religion. Therefore, at least 37% of Russians practice some form of religion with sincerity. This means approximately 63% of Russians (not 99%) are either atheistic or simply non-practicing, but still claim to adhere to some form of religious belief. 63% is certainly still a lot, but it isn't 99%.
This post is not meant to demean or belittle efforts to evangelize inside Russia, either by foreign missionaries or Russian Christians themselves. However, we shouldn't present exaggerated numbers when trying to win people over to the idea of missionary work. Let us who serve He who is Truth speak with truth.