No idea how you get the impression SOE wanted PS2 to be some kind of million player wow killer caliber MMO or anything like that. The game launched with no tutorial, hardly any marketing and has had huge re-designs of core game mechanics and more to come, mostly at the behest of the players. It's always seemed to me to have been a test run for the new Forgelight engine, and a test run of how a AAA-developed MMOFPS with a F2P money shop would fare in todays market. Hint: It did pretty well.
Edit: Population wise, 70k gets hit when they have a bit content patch and tie it in with double-exp weekends. Otherwise it's usually around 15k-20k, and probably dipping due to August school starting, FFXIV, etc. I've been playing since May and am pretty much done with it waiting for FFXIV now, play it for 3 months, then hope EQNL beta gets put out around Christmas.