[Wuli]

Reagan had warned Europeans about them getting into bed with Russia on energy, about how Russia would try to use it as leverage in matters against western European interests.

[Mogger]

In this case, isn't it Ukraine that cut off the gas by not renewing the agreement on the pipeline through Ukraine bringing gas from Russia to Germany?

Of course the effect is the same as if it was Russia that cut it off.

Either way, Trump was right about relying on a single supplier, especially in an area historically volatile.