What, nobody really knows? Fine, I'll explain it then (it's really simple).
Apple is moving away from Motorola processors and toward Intel's products. The Intel chips are faster, and the move to x86 will allow for greater application compatibility in the future. Basically, Macs are PCs now and OS X is just another flavor in the PC OS market next to Windows, Linux, BSD, SkyOS, etc. All of a sudden, porting PC apps is easier...more sales for Apple.