[reeredfdfdf]

The pipeline thing may have annoyed Russia, but it was the Maidan revolution which resulted in the invasion of Crimea. Russia simply doesn't like having neighbours that aren't its puppets. When Ukrainians got rid of Yanukovych, Ukraine stopped being a Russian puppet, which annoyed Putin very much.

Russia has a long, long history of being mean to its neighbours that choose to pursue independent policy. As an example, Finland and Baltic states have been subject to countless of intentional airspace violations since the collapse of the Soviet Union, even before the Ukrainian war.