They are primarily interested in money and power. The homosexual movement is most directly tied into the leftists, and not only does control of the money and power allow them to advance the homosexual agenda, but also the leftist agenda as a whole (eminism, environmentalism, pacifism, one-world government, etc. etc.).
Most mainline denominations, because they are old, have both valuable real estate (in large metropolitan areas) on which their churches were built years ago (think of the Episcopal church of St. John's across from the White House); in addition, over the years, they have been recipients of land and other valuables bequeathed to them by grateful members.
Some churches also own universities (Southern Methodist, for example).
You are right that they probably shouldn't be that wealthy. I think many of the churches have used income from these properties to fund worthy endeavors. However, should the hierarchy change, I do not think the money would go to the same causes.
Don't forget that the homosexual group are the wealthiest in America. They generally pair up into couples, have two disposable incomes and no children, more disposable income.
All future bequests will now have morality clauses.
You hit the nail on the head with the money. (same reason they don't go and form their own boy scouts.) It is not the one homosexual priest becoming a bishop, its the other homosexual priests pushing him from behind. This was a done deal looooong before the vote.
They are counting on the backlash being nothing more than words. I hope, regardless of the silver involved, that the people back their objections with action.