Except
1) Apple weren't the first innovating in that regard. I don't know who was, I just do know Nokia was experimenting with Nokia 770 and Nokia N800 in 2005-2006. True, they weren't smartphones, but they were going in the right direction. Without many buttons. The Nokia N810 had a keyboard, and that was less well received than its N800 keyboardless counterpart.
2) Apple didn't remove all buttons from the iPhone (power, volume keys were still there). The two important changes were:
A) Removal of the physical keyboard, replaced by a (by then) well working OSD. Working with a capacitive screen.
B) They made 1 main button.
Sure there were other smartphone, Apple wasn't the first, etc But thinking that people would just go 180 was just extraordinary. Apparently people were ready to sacrifice quite a lot for the huge screen of the iPhone.
Leader where? Blackberry was never the marketleader world-wide. That was Nokia, and OS-wise it was Symbian until ~2010 when iOS and Android took off. Nokia was never very popular in US though.
> and the keyboard was his best loved feature.
Sure.
Because on screen keyboards were still using resistive touchscreen with pens. Which is a terrible user experience. Apple used capacitive touchscreen instead, and even though the resolution was low, it worked.
Nokia didn't invest enough in Maemo, and didn't want to adopt Android either. When they finally did go with Maemo, Elop came with plan A. Look at the user experience of Sailfish. That could've easily been Nokia in ~2014...