Apple is known for innovating, and being the first to release a big product or feature. However, in this particular case, they were beaten by Samsung, who had produced a phone with a large screen before Apple did. Naturally, if Apple had been the first to release a large screen phone, it would have set them apart. Right now, they are trying to catch up.
I think Apple needs to better keep up with what their competition is doing. They can only ride on the brand recognition and "loyal followers" for so long. Every year they're going to lose customers to makers like Samsung, who create phones like the Galaxy S5 that are much bigger than the iPhone and have capabilities that Apple still isn't providing in their phones. If they create a more competitive product, they'd definitely give the competition more to be worried about.
While it is unfair to say that Apple missed the boat, the size increase clearly had appeal to a lot of consumers. In particular, adults with money to spend who had trouble seeing the smaller screens in the past have welcomed the bigger screens. While the bigger phones are bulkier, they allows easier use of the touch capabilities, and Apple should have seen that coming.
A few years ago people were complaining about large screens and then screens got smaller. Iphone is just going long with society. The society likes larger screens now, so Iphone is giving them larger screens. They would have had the same amount of money, if they started off with large screens.
I don't think having a larger screen three years ago would have increased IPhones market share. Large screen devices have only really become necessary in the past two years, as peoples data usage, and speed of downloads has increased. I do feel they should have released it a year earlier, as rivals such as Samsung and HTC were releasing their "Fablets"