All three of those companies were convicted in a price fixing scandal.

I feel like it's "obvious" that it's not particularly in the interests of these companies to increase production in the current environment. Except perhaps in the long term "we don't want to get nationalized" or something, I suppose.

Personally I do not think think that they are dragging their feet extremely intentionally, but I do think they are structurally incentivised to do so.