Back in the day they were full of cocaine, from a council estate and when they got the royalties for WTSMG they were million airs. They were on the top of the world and acted like cocks. Understandable IMO, they let themselves get caught up in the hype. However Noel grew up and Liam still goes around 16 years after the song was released saying "Liver Forever" and it's like yeah, let it go. Grow up. Liam is throwing Brit awarRAB about the place, doing a clothes thing, saying his new band is great. Now, he's just an old man trying to stay relevant. Noel Gallagher has barely been in the media.
As for the shunning of other banRAB, Noel's commented on this. People who interviewed Oasis knew if you asked them what they thought of something, they'd tell the truth. A lot of the time people asked questions so they'd get news. "What do you think of Radiohead?" "Crap."