Xerox didn't give a shit about dominating the market with a GUI-based personal computer. The laser printer
alone made enough money to bankroll all of PARC's operations and then some. Everything on top of that was pure gravy.
Google is, and Xerox was, seeding ideas the way VCs seed companies: all they need is one or two that hit the jackpot and it'll all have been worthwhile. If the others aren't fully ripe yet, maybe they'll ripen in time and under other management; it's all good as long as the parent company ends up in the black somehow.
If PARC's GUI research were a business boondoggle, then so is every corporate contribution to open source.