Owners or residents elect condo boards. Once elected, the board does have a degree of control over the operations of the condo building. However, condo boards are restricted by the condo corporation's governing documents—the aforementioned declaration and bylaws.
Accordingly, different condo properties afford their boards different levels of power. But, ultimately, the board answers to the owners. If board members are overstepping their authority, owners can vote to remove them from their position.
In fact, owners and other residents often vote on issues directly, rather than the board acting independently. Budgets, bylaw amendments, vendor contracts, and many other things typically need ratification by condo owner votes.