I've never seen a crowd not applaud the vets, and given the bogus obsession philly people have about being working class heroes (despite having no claim to that whatsoever), nothing else would be expected. The bigger the crowd, the louder the ovation. Also, philly fans are all a bunch of overgrown teenage beta males. They're all followers, like the little dog who follows spike around in the cartoons. They all just go with the pack. No matter what it was as soon as it looked like the rest of the crowd was cheering they were all going to follow suit.
Regarding the WWII vet, I think the Nats PR department deserves to get bashed. They introduced that guy and then he was stuck standing by himself out on the mound for minutes not knowing what to do while being ignored. It was sad. Finally the umps went out and shook is hand and chatted with him. He just looked like some lonely guy standing out there like nobody cared. Epic fail by the Nats game operations team.