Where oh where did Microsoft get the idea to totally rebuild their mobile OS around the concept of a full-face capacitive touch-screen?
Yes, they were resistive rather than capacitative touch-screens. That wasn't because it didn't occur to anyone to use a capacitative touch-screen before Apple, it was because the technology wasn't mature enough before around 2006/7. And if even you want to make the (silly) argument that whichever manufacturer happens to be the first to bring out a full-face capacitative touch-screen phone can somehow claim to have invented the concept, that honour goes to the LG Prada.