It's the demographics, with high Muslim birthrate and immigration rate, versus the much lower birthrate (well below replacement levels) of native Europeans. Russia has been reversing its negative demographic rate from the Soviet era, but still faces an uphill battle.
Orthodox Prelate: ‘Europe Will Turn Muslim’ in 30 Years, Christians Will Live in Secret by Michael W. Chapman, CNS News, May 18, 2017:
 |
| Archpriest Dmitri Smirnov, chairman, Patriarchal Commission on Family Matters |
Speaking on Russia’s Soyuz TV on May 5 — translated by the Middle East Media Research Institute (MEMRI) — Archpriest Smirnov said, “There is very little time left until the death of the entire Christian civilization. Several decades, perhaps 30 years, well, maybe in Russia it will last 50, no longer.”
“And then,” Christians “will be like peas scattered across European countries,” he said.
 |
| Muslims pray in the streets of Moscow... |
“Christians will not dare stick their necks out,” said the archpriest. “They will congregate in small groups and will be persecuted. the rehearsal is already underway. In Europe, Christian women are being raped and murdered, and the men who are forced to protect their women are unable to do so, while rapists are sentenced to one-year probation maximum.”
“This goes on in Europe and we are next in line,” said Fr. Smirnov.
Concluding, he remarked, “In three decades, the whole of Europe will turn Muslim and Christians will live in a semi-underground” existence.
Russia, the largest country in the world in terms of land mass, has about 59 million people who adhere to Russian Orthodoxy. There are an estimated 9.4 million Muslims in the Russian Federation. The total population is estimated at 144 million.
 |
| ...and in front of the US Capitol |