A huge portion of the fanbase is lgbt. Understandably, when it was confirmed that a LEAD was canonically queer this whole time, many of said lgbt fans (myself included) were ecstatic to see a character we had looked up to for years represent us.

Then, not even a minute later, he died to save one of the other leads -- and I won't even begin to explain why Bury Your Gays is problematic as others have done it much more eloquently. His sacrifice was hardly acknowledged, his contributions were forgotten, and his loved ones cast him by the wayside. When Dean got to Heaven, Castiel wasn't even a blip on his radar. Cas got no recognition -- Cas never once heard that he was loved.

I recommend you do some research into why these disturbing media patterns are harmful to lgbt folks. This is queer erasure, plain and simple.