To be clear, while you are not required to give a flying fig about whether or not Exxon investors earn a return, you can't exactly expect them to all line up to gleefully throw their money away, either. That's a charity, not a business.
And trust me, if we compare the financial returns on investment for renewables and nuclear technology over the past N decades, versus Exxon's returns today? Definitely not a win-win.
If they had started investing back then, they'd likely be in a better position today and going forward. A leader in future fuels instead of clinging onto fossil fuels, which is definitively short sighted.
There is no financial case to be made here whatsoever.
Now, going forward, in 2020, there might be a different calculus. Usually, the market cap/stock price of a company reflects future cash flow. For an E&P company, much of Exxon's valuation comes from the cash flow expectation on its oil reserves. That's problematic if some of those oil reserves are in effect stranded assets. Certainly not all will likely, but say, things like the tar sands? It very well could be.