These are not mutually exclusive. You can, in fact, do something that financially benefits you and creates a general good in society or culture. Dancy clearly believed the OGL would do both (and I think evidence strongly suggests he was right).This is plausible, and was part of Dancey's rationale for the OLG - ie contra some recent posts it was not "altruistic" but rather a calculated method of increasing WotC's market share and profits.
This aspect is what i think got many of us so irritated with WotC when all this started: there was no reason WotC couldn't continue to see record growth and profits, and at the same time maintain the good that was Open Gaming. They actively chose to burn down Open gaming. We just don't quite know why yet. I'm assuming greed and hubris, but it is possible someone had a legitimate (if ill conceived) plan.