Schröder's actions were only marginally less embarrassing than Trump's Helsinki performance.
In Germany it is totally normal that former politicians switch sides and get high profile jobs in private corporations, often as influencers.
Even active MdB / Abgeordnete could earn millions, they only need to publish the rough dimension of their earnings.
As former chancellor, Schröder is granted a free office with Secretary in Berlin payed by taxpayer money about 0.5 M€ annually, and there are initiatives to abolish this service because of his Gazprom connection.
The strong connections between private economy and government is seen as a key success factor for Germany‘s economy, called Deutschland AG in the 1970‘s (Germany PLC).
https://de.wikipedia.org/wiki/Deutschland_AG https://en.wikipedia.org/wiki/Gerhard_Schr%C3%B6der
There are some exceptions to that such as weapons and nuclear products, but gas isn't one of them.
It's such a bad plan on many fronts, that I really struggle to understand how an otherwise pretty rational political culture arrived at it.
It is an old German (and Austrian) problem, which actually predates Chernobyl by at least a decade. Targeted Soviet propaganda might have played a role; Soviets were very interested in getting Allied nuclear weapons out of West Germany. Spreading all kinds of FUD about the "Atom" in general was a way to cultivate public opinion towards that goal.
Just look at what other politicians do. Gazprom, Palantir etc. are good employment opportunities.