While Russia hasn't been a part of OPEC, so wouldn't be the cause of OPEC only now failing to maintain a cartel, it's important context to know that Russia and OPEC frequently collude on oil price manipulation together via OPEC+.
For example, last month: "Oil prices edged higher on Monday after top exporters Saudi Arabia and Russia reaffirmed their commitment to extra voluntary oil supply cuts until the end of the year."
