The problem isn't that it's particularly hard or risky to dismantle the bridge. It's that this specific bridge is an industrial monument that holds a special place in many people's hearts and after the last restoration in 2017 a pledge was made that the bridge would never be dismantled or otherwise harmed again.
Then along comes Mr. Rich Man with his exorbitant needs and suddenly these promises have all become worthless. It's a matter of principle; people are fed up that the rules never seem to apply to the super rich and everything and everyone has to make way for their demands.
Why would you build a bridge that can be opened up and then promise never to open it up again, especially when there’s a shipyard on the other side of it? That makes no sense.
Because it doesn't function as a bridge anymore. It stopped functioning as a bridge back in 1993. It's a monument now, an industrial monument and part of the city's heritage. It's already permanently in the open state and more than high enough to let almost any ship through easily. Except for Mr. Bezos' new superyacht. That's why it would have to be dismantled.
It's a bridge for trains that now use another track, and it is permanently 'open' for normal shipping. Bezos' toy isn't a normal boat so they have to dismantle it, which includes lifting out the movable part in its entirety. This is not without risk to the structure, as has been proven in the past.
Then along comes Mr. Rich Man with his exorbitant needs and suddenly these promises have all become worthless. It's a matter of principle; people are fed up that the rules never seem to apply to the super rich and everything and everyone has to make way for their demands.