no team started Australia's fall. the retirement of key players started Australia's fall. how exactly do you replace mcgrath, warne, Gilchrist, Hayden and langer. these players were the best in the world at what they did.
India, no matter how well they have performed over the past 5 years or so, are unfortunately an average team with 2, maybe 3 above average players. You look into their record and see how they have failed to perform on several occasions. A good team can play poorly and STILL win. Australia had that.
The Australia team of the 90s/noughties was a team with good players. Now its just an average with 4 above average players (RP, MC, Lee and The Huss).