They've expressed anti-competitive behavior from the beginning, but it's advanced over time. It's the confluence of factors that makes it particularly bad in Apple's case. You can't chance the software (OS) on the device. You can't run iOS on a different set of hardware. You can't run any store but the App Store on iOS. You can't deliver software to customers without using the App Store (or jumping through hoops for very limited methods of getting it on there otherwise). It's not that 30% was ever good or bad, but that initially there was no competition, and at every step Apple has taken steps to make sure competing is extremely hard to do, by tying you to an entire ecosystem.
Android is better in some respects, but is mostly happy to not actually compete on a lot of levels because that would possibly endanger the 30% industry standard. What we have is two extremely large players, so large and so establishes and in a market that takes so much money to enter that new competitors are at an extreme disadvantage agreeing, even if tacitly, that the fees for their stores are not something they will compete on.
That's not better than when they agreed they wouldn't hire each other's employees (which they were punished for). It benefits only themselves at the detriment of everyone else, and through market manipulation. If they actually cared to compete, we would see competition in store fees.