Serious question because I never had any handhelds back in that era, but what made the Vita suck? I've heard there's some great games on it despite opinions about the console and it's always been unanimous that the PSP was great, but how did Sony screw it up? Not going out and buying either one right now, but I never really see specific reasons mentioned.
They dropped the UMD drive and replaced it with that gimmicky rear touchpad thing is probably the biggest reason.
They dropped something incredibly functional and would have given the Vita access to the entire library of PSP games at a time when it needed that library the most to compete against the smartphone (Vita was released in 2012)
I think the 3DS/DS were able to remain dominant so long even in the face of strong competition from the rise of the smartphone was because of the deep library of older titles to keep it going forward.