His direct involvement with the Russian oil and gas sector (and, most likely, influence on their behalf) is a lot more recent than just 'the 2000s' [0][1].

[0] https://www.cleanenergywire.org/news/ex-german-chancellor-sc...

[1] https://de.wikipedia.org/wiki/Gerhard_Schr%C3%B6der#Rosneft