Ill use Valkyria Chronicles 2 as an example.

Why do developers have a franchise that established on one platform and instead of making a sequel to the game on that platform, or waiting for the next version of that platform, they put it on a different one and maybe alienate their audience?

I mean Sega explained why VC2 was on the PSP I understand but other franchises don't make sense. I can't really think of an example right now but I seen it multiple times.

I mean if it was to attract a new audience why put the sequel on the system and not the first one?