BlackBerry lost it because of hubris. They thought they were the best and didn't need to change. They realized too late that they needed to do something better. By that time they had started to lose market share. They held firm to the line that market share did not matter because the profits were there. By the time the dust settled, their market share was too small for developers to care about them. And thus started the death spiral.
Is Apple there? Not yet. But Android owns a whopping 88% of the phone OS market, with iOS at around 10%. That's still a significant share, but not where they can rest on their laurels.
Android market share doesn't really matter because most of that market share is made up of really low quality devices that are bought by people who will never pay for an app. Hence it doesn't really matter to the developers. It's a fact that developers make more money on iOS vs Android.
A only possible way of making money on Android is using adverts within free apps. And the only way even that model works is if the app has millions of users which is again mostly only attainable by huge corporations with millions to spend for advertising. Therefore smaller developers genuinely don't care about about how much market share Android boasts.
Ps. Blackberry never had as much developer followers compared to what we are used to these days. There were only handful of apps available on blackberry even when they were at their prime.