His speech also came after Europe already realized that in 2014 when the Crimea was annexed [0], and countries didn't want to go too hard with sanctions cause of the dependency. The obvious motive for the speech was a desire to sell US gas to Europe.
[0] For example see a policy brief from the european parliament in 2014: https://www.europarl.europa.eu/RegData/etudes/STUD/2014/5364...