When oil prices are down, little is invested for new production, maintenance is cut to the bone. Sometimes they sell off stock to stay alive. When the price goes up, so does the spending. The oil industry has always been cyclical. Those who don't prepare for the coming bust usually have their assets bought up by the ones that did.
If you really believe they are magic money machines, you ought to buy their stock and retire early.
The numbers are not absolute but expressed as a percent of sales.
In an inflationary economy where the sales price of oil and energy is rising, the absolute earnings are increased thus making the stock a good deal in an inflationary economy.