Conventional wisdom is that “The Saudis have kept their production levels high since last year in order to drive other players (especially U.S. shale drillers) out of business.”
That is a very simple way of looking at it, there is an alternative theory that the Saudis are keeping prices low to destabilize the Iranian economy and weaken there insurgency actions in the regions, specially in Syria and Yemen.
There’s also the theory that the Saudis are not keeping prices low, but the market is.