Why did the Wikimedia Foundation hire Q2 Consulting for a study?

That's certainly what it looks like on the surface, though I'd probably call it "deliberate avoidance of" instead of "failure to solicit."

If so, it's the classic sweetheart deal - those donors can only hope that the Foundation got a low-ball price on the study from Q2 Consulting, since a small outfit like Q2 would probably gain a fair amount of prestige by being able to put an organization that lots of people have heard of on their collective resumé(s). And if the Foundation ever has to cut back on staff, Beaudette can go back to Q2 knowing they've benefited from the extra media exposure, thanks to him.

Of course, when it comes to market and donor research, you tend to get what you pay for!

Cronyism. It happens all the time in government, too.