I suspect that the recent decision by OPEC not to reduce oil production is to bring pressure to bear on Russia to get them out of Ukraine.

Russia is heavily dependant on oil exports to support it's economy. It needs that money to pay the wages of public servants, to pay the monthly pensions of it's large population of senior citizens and to import food because of an agricultural industry that's on life support. Without that income, there could be civil unrest in Russia, and that could break Putin's grip on power as people there demand a change in government policy. With the recent drop in oil prices, Russia is even more dependant on maintaining it's level of production to keep the money from oil exports coming in, and as long as Russia won't reduce it's oil production, OPEC is not likely to reduce theirs either.

I suspect that the West (the USA, Britain and the EU) convinced Saudi Arabia to maintain it's current levels of oil production to bring pressure to bear on Russia to get out of Ukraine.

It's just a guess, but it's my best guess.