They see the writing on the wall. While there is still a lot of petroleum, coal, and natural gas (PC&G) in the earth, it is finite. Sun, wind, and water, however, are nearly endless in supply. Where PC&G are endangering the planet and our very existence, renewable energy is nearly harmless. Technology is advancing with such a rapid pace that it is far more cost effective to use renewable energy than ever before and it is only getting more cost effective. Add to it the government subsidies for renewable energy as well as investment into businesses and new product development, it only makes sense for traditional PC&G companies to begin to plan for life after PC&G. The best way to do that is to begin merging and acquiring other businesses.
Certainly, there is some number of PC&G businesses that have the ulterior motive of acquiring renewable energy companies with intent to quash their growth but such actions will only postpone the inevitable. In the end, PC&G will see significant reductions, though I highly doubt they will ever go away, while renewable energy will simply grow more prevalent. The strategic energy business will make their acquisitions now and plan for the future.