It was founded to allow a place for free, frank, and civil discussions between people from across the political spectrum and modeled in large part on old school SB.
As for why it was founded? Because SB does not allow free and frank discussion of contentious topics, punishes wrong think, and has a staff that is perfectly happy to thought police and make up rules to get the outcomes in discussions that they want. SV is a lawyer RP that, politically and in terms of rules enforcement, makes SB look sane. QQ has their Rule 8. And AltHistory is Ian's little insanity playground.
Now for why we got a ton of people? Well that is what happens when SB proves itself actively hostile to a large swath of its user base and the SB Mods and Admins actively break their own rules to allow harassment of said users. Well that and we started with a large number of prominent people from SB (and a few other places) involved.