Warren Buffett/Berkshire Hathaway bought more OXY on July 5th and 6th

Not too far from its ATH. Not usual for them to buy a stock unless they find it undervalued. Does anyone have any insight on this?
I go first. I guess they find them undervalued. They must be optimist about the price of petrol&gas in the long term. WB mentioned that he decided to buy when reading the earning report of Q1, and thought that the CEO was doing all the right things.

But they know hold a significant share of the company (don't forget the preferred and warrants), and keep buying at a high rate (they bought ~1% between yesterday and Tuesday). At this rate, one wonders if they are thinking of buying the whole company, which is what they always said they prefer to do.

However, contrary to what one might think when listening to Buffet and Munger, they often sell stocks after about 6 months, and they have "played" cyclicals before (PetroChina, famously).