It had just the right amount of skeuomorphism, without going overboard; probably because of hardware limitations.
What I think happened is that as computers and phones got more and more powerful, developers and designers wanted to use the UI to show off a bit. Culuminating in mad animations like a shredder destroying your old boarding pass in Apple Wallet.
Then there was a complete rejection of skeuomorphic design with iOS7, and it's just got more and more extreme since then.