Lithuania claims it is simply abiding by the sanctions imposed by the European Union. After all, Lithuania is a member of the European Union and NATO. But that is the point. This is a deliberate provocation. It is laying economic siege to a vital interest of Russia. While there is no immediate danger to the Russian population of Kaliningrad, this is a flash point that could lead to an actual war as opposed to a special military operation.
What is the difference between a special military operation and war? In the SMO you leave communications, electrical infrastructure, transportation infrastructure and fuel depots largely intact. In the SMO you try to minimize civilian and military casualties.
War on the other hand is terrifying. If Russia opts for a war footing, the restraint that characterized its activities in Ukraine will be replaced by a full-on attack on key military installations and assets in the region as well as the destruction of the communications, electrical, transportation and fuel resources of the adversary. This probably includes taking out critical satellite communications and intelligence collection systems of the United States and Europe.
Kaliningrad, formerly known as Königsberg, was put under Soviet control in 1945 according to the terms of the Potsdam Agreement, which was backed by the United States and Great Britain. The Russian people paid blood for this land in 1945 and are not going to relinquish it in the face of bullying or threats from the west. If you are going to poke an angry bear with a stick, you better be damn sure that bear is locked up and can’t get you. Russia sure as hell is not secure in a cage.