"Largest war in Europe" is the key phrase here.
Latin America, Africa, and the Middle East all have ongoing military conflicts due to Western interference and proxy wars. Why not another one?
And both France and the U.K. backing this is laughable.
It's less a bluff for Russia than it is a strategic maneuver to either ensure they have strong support on their orders or to force the hand of NATO (i.e. the U.S. and U.K.).
Ukraine has a long history with Russia. It was a part of the USSR. After the collapse of the USSR, the United States began pushing for strong relationships with former Soviet-bloc countries, and "joining NATO" was the easiest way to do it. That then allowed them to bring them into the financialization fold, and also allowed them to gain a strategic military advantage. What is very rarely talked about is that after the "fall" of the USSR, the new economy introduced by the West led to massive issues with these countries' economies, and the quality of life dropped massively - Ukraine was one of these countries. A huge chunk of it is ethnically and linguistically Russian, and that chunk wants to retain ties with Russia. The other portion of the country isn't and wants to join the fold of the Western European nations.
The U.S. is pushing for the country to join the West, has armed and trained some of the right-wing and neo-Nazi portions of Ukraine, and as such - has directly implemented the split.
Russia wants control on their side.