Many birds don't have the greatest sense of smell and also don't pay attention to stuff like predator urine (really? On a coaster forum?). They will give up on building the nest eventually, especially if they are disturbed enough. Right now, it's a high vantage point that is protected from land predators (I am guessing that they don't know that velociraptors can climb) and thus a seemingly great place for a nest. It might not even be the same osprey pair. It's probably a shady Osprey Real Estate agent who keeps marketing the location to young osprey couples looking for a starter nest.