That's the saddest part - there were probably real 5k+ on each Talking Island and Giran when it started, and even though many would've left naturally because Classic isn't for them, there still could've been more than double the active players we have right now if NCsoft didn't take so many wrong steps. But in short, it required two main things:
1. Hire more GMs to guard the main spots. Pay them overtime, too. If the GMs are active enough and botters need to make new chars every few hours, many of them would've just given up. Sure there'd still be some, but it wouldn't be such a botfest it is now - I mean ffs, it was the first weekend after launch and neither Hime or Juji logged because fk it, it's weekend, ain't working. Paying them and the GMs (which don't exist) would've been an investment to retain more players.
2. The damned rates. It's just a clown fiesta at this point, but a week after launch it was apparent that absolute majority of players hate the rates and are not willing to suffer them in longterm. It was the awful decision to keep postponing it (until they ultimately took the wrong decision anyway)
But it's just messed up. Most people just left to illegal server, some of them left back on a different chronicle servers, some unfortunately just gave up on L2 completely.
NCsoft should be added to dictionary under "wasted potential".