I agree that Nintendo's leaders are sharks and no what they are doing (most of the time) in the gaming market.
However, as far as Sony in the mobile market, it made perfect sense for them to enter it. It made Nintendo lots of money, why shouldn't they take it like they did the home market? The problem was Iwata took over Nintendo and they dramatically shifted their approach to making games and systems. They mixed back to basics(ieNSMB) with innovation and non-gaming projects (ieBrainAge) with a cheaper, more innovative pure gaming device. PSP did well, just not well enough. A big part of the problem is that the approach used in home consoles doesn't work as well on portables.
As far as Vita goes, it isn't so much losing to Nintendo as it is losing to other multi-use devices. 3DS is holding ground because it is a cheap, pure gaming device that is kid-friendly and offers Nintendo's software. The role that PSP held has been replaced by other mobile devices.
