Long Island College Hospital in Cobble Hill died last week at 156 years old after a long illness caused by rapid changes in the city's health care-delivery system.

LICH is survived by an active emergency department on the site and by an empty hospital campus with harbor views -- a place now ripe for housing development.

The death is a pointed rebuke to Mayor Bill de Blasio and his leadership style -- but not because he failed to save the outdated medical behemoth.

Nobody could have done that -- not the local politicians who rallied on LICH's behalf, not the health care unions that ran to the ramparts, and not the local activists who hated to see a respected neighborhood institution go.

De Blasio fell short because he failed to face the truth.

While LICH was bleeding tens of millions of dollars a year from the state university system, de Blasio behaved as if the hospital was in jeopardy simply because greedy developers wanted the land it stood on.

As a mayoral candidate last summer, he managed to get himself arrested at a protest rally to save LICH.

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And in late February he took a victory bow at a rally along with other activists after the state announced it would try to find a developer willing to build a full-service hospital on the LICH site, a mission that ultimately failed.

Here is the problem. By late February, de Blasio had been mayor for almost two months. He was no longer an activist-gadfly-politician. If he didn't grasp that LICH was doomed as a full-service hospital, he should have.

He also should have known that it's not always wise to lead a prolonged campaign for a plainly hopeless cause. That's especially true when the cause is LICH, which was threatening to wreak havoc on SUNY's own budget as the dickering over its fate dragged on.

Today the mayor is still declaring victory -- although the LICH site will likely end up with the very outpatient services that advocates had opposed. He needs to try a new tack. We're hoping he'll eventually drop the protester pose and act like a mayor -- by charting a savvier survival plan for the city's other endangered hospitals.