That's the key: they hate losing market share. However, the presently most widespread renewables -- on-shore wind, rooftop solar --, especially when paired with a feed-in law, are structurally predisposed to bring in many new small owners and thus break monopolies. The energy giants will (do) like off-shore wind much more (not to mention centralised solar power, hence the support for the IMO pie-in-the-sky Desertec). But, even when existing energy giants build renewables, they will be less enthusiastic about an accelerated replacement of their existing plants, though.

_{*Lunatic*, n.
One whose delusions are out of fashion.}