What about Persona 4 sales? How do you explain they are lower than 1? Where was the new audience then? I don't see any reason why P5 would sell 400k+ LTD in Japan all of a sudden.
Are you seriously having this discussion or are you just taking a piss? I will assume that you are serious any take the time to educate you. Persona 1 was a RPG released on the PS1 in a time where pretty much anything can find great success because the market was exploding. Both Persona 2 games couldn't perform at that level, so it's obvious that the success of the first game didn't indicate the size of the franchise fanbase at all. In fact, after the second game, the Persona series was put on ice.
Persona 3 came out 6 years after the second Persona 2 game. It was on a brand new platform, it had a brand new core team behind it, and it had a brand new style. The gameplay flow is radically different from the previous games and it was targeting a new younger audience. This was essentially a reboot for the franchise and the story had no links to the previous Persona games, unlike the first 3 releases.
From then on, Persona has been building the new brand. Persona 3 sold 196k. Persona 4 sold 335k, Persona 3 Portable sold 232k, and Persona 4 The Golden sold 332k. The budget re-releases for the games sold very well too. Persona 3 Portable's budget title sold over 100k.
Meanwhile, the PSP remakes for Persona and Persona 2 did not go as well. Only Persona managed to sell over 100k, with the subsequent Persona 2 releases selling much less. This shows that there really isn't that much interest in the old games at all from today's Persona audience.
What we are looking at is a rebooted series on a growth track and is expanding, not a series that is recapturing old fans who somehow stopped buying the series. The demographic of fans for Persona today trends young, and many would not have been born yet when Persona was first released.