It's realistic. Russia needs to sell natural gas to finance state activities, Europe needs natural gas to not freeze in the winter.

Russia can only play with natural gas diplomacy to Europe to a limited extent, because Europe is their main market and they don't move much into China (the PRC gets gas for cheaper out of the Stans, so not a great market for Russia). That's why Russia uses it pretty selectively against countries that are weaker (Poland, Ukraine, the Baltics). EU could counteract this by forcing a union-wide buying cartel, rather than letting countries negotiate working with Russia individually.

EU countries have been trying to get alternate routes up and running, but Russia has been pre-empting this with some maneuvering (any plausible route would go through Turkey, Syria, or Iraq)