Merkel had and used actual leverage. Perhaps she said that Germany was willing to forego Russian gas even if it meant buying LNG at exorbitant prices, knowing that it would cause hardship for Germany but the end of Russia's economy. Russia depends more on Germany than vice-versa, and Putin knows it.
In other words, Putin respects Merkel and Germany. In contrast, he brushes Obama off like a piece of lint.
And SHE knows it, and has the stones to USE that fact.