Not source, supplier.
Take your pick^^ The factors are blatantly obvious.
Threatening to cut off supply. - This was in direct response to sanctions. i.e. A response, a Reaction rather then an Action.
Actually cutting of supply to Poland + Bulgaria. - I'm not quite sure what action led to this, happy for someone to chime in.
Demanding gas is paid for only in Rubles. - This was in direct response to sanctions. i.e. A response, a Reaction rather then an Action.
Reducing supply in NS1 to 40% in June. - This was in direct response to sanctions. i.e. A response, a Reaction rather then an Action.
"Halting the operation of one of the last two operating turbines of the Nord Stream 1 pipeline due to the “technical condition of the engine”." -
https://www.aljazeera.com/news/2022/7/26/explainer-nord-stream-1-gas-pipeline-russia-germany-europe - This was in direct response to sanctions. i.e. A response, a Reaction rather then an Action.
And oh I don't know, invading the most important transit country of energy supply to Europe. - After a foreign power removed the elected government there back in 2014.
That is only scratching the surface.
Do you believe Russia has the reputation of a reliable supplier of energy to Europe? - Before this war Russia supplied energy. Russia stopped supplying in direct response to actions taken by the west. in this regard the West has not been a reliable trade partner.
If you do, what factors lead you to believe that?