McCain got his picture and hagiographic coverage in a liberal magazine. Mission accomplished. He’s admired - but only temporarily - by the left not for being a war hero but for throwing an election to obama. And his heroism ended when his chute landed in NVN. After that, it appears that he had to be babysat by cellmates who were genuine heroes before and during captivity. If the truth be known, his own admitted cooperation with NVN would be the real reason the left considers him a hero, despite the fact they secretly considered him a baby killer before being shot down.
That's a big part of the story, but the main reason McCain is so well-loved by liberals is that he has consistently put more effort into undermining conservatives and conservatism than any other prominent Republican during the past 20 years. McCain could barely bring himself to criticize Obama in 2008 (much less during his Presidency), but he's all fight, spit and bile when there's a conservative or nationalist like Trump to attack. Mitt Romney is cut from the same cloth, but never quite got the same love from the media.