Walk the halls of the finest UO yeshivot in the world, especially the ones in America, and you wouldn't be able to help but notice that the money isn't coming exclusively from Orthodox Jews; not by a long shot. This phenomenon begs interpretation. What would move a person to contibute vast amounts of money to an institution which espouses values that he does not? To take a sharper example, why would someone fund a lifestyle - let's say a kollel lifestyle which isn't viewed as training for eventual participation in the broader community - that he doesn't even condone?
I'm sure there's no pat or simple answer, but I think there's a pathos which motivates the contributor and includes one or more of the following elements:
1) Guilt. The famous 'here - you go ahead and cross your father's name off the list' story involving R' Kahaneman is the prime example of this. The prospect of bankrupt institutions, hungry families, a world without Torah or Rabbis or Orthodoxy can have a very powerful effect on someone.
2) Buying a Slice of Heaven. For many non-Observant Jews whose Jewish worldview is still shaped by Orthodoxy, donating to a Yeshiva is like buying shares in a divine stock. It's not quite the sale of indulgences, but, needless to say, it doesn't reflect a very mature worldview.
3) Nostalgia/Perceived Authenticity. To my mind, this is the most powerful and effective (and untrue) element of successful Chareidi fundraising. There's this myth that's being successfully perpetuated by Chasidim (esp. Chabad) and Chareidim that the more distinct one looks, dresses, speaks, and thinks, the more 'authentic' their Judaism. In Me'ah She'arim, there are 'real Jews', like it oughta be! For second-generation Americans who yet remember the European generation, and who feel a strong nostalgia for their grandparents' Judaism even though they themselves haven't kept it up, contributing to institutions that they percieve to be the continuation of 'Zaydie's' Judaism can be very comforting. This is Chabad's bread n' butter, it's everyclean shaven 'g'vir' sitting next to the Rebbe at the tisch of whichever Chassidus, and it's much, much, more.
This latter attitude is the bane of serious, halakhic, non-Chareidi Judaism. For so much of the Jewish world, across the spectrum, UO is the standard by which the authenticity and validity of everything else is judged. Obviously, the fundamental flaw is in relating to UO as the continuation of the way things have always been and not as an invention of the last 1.5 centuries, like everything else on the contemporary scene (NOTE: that's not to say that all form of contemporary Judaism are equally 'authentic' , 'valid' 'legitimate' in my mind, simply that they're all roughtly the same age, and authenticity is judged by criteria other than age).
But we're not really talking about ideology; we're talking about marketing. And in that respect, they've done a good job.