Tabula Rasa came out at a weird time for MMOs, a few years after World of Warcraft, which basically took the genre mainstream. Before WoW we had things like Ultima Online that were "massive successes" for having a few hundred thousand people playing.
Tabula Rasa was also Richard Garriot's go at another MMO after Ultima so it was a big thing, at least for players of UO. It was a great game that offered something completely different to what was on the market and had that Garriot charm of him killing all players at the end of the beta. As is tradition. It's demise was essentially for the same reason all of the other MMOs that came and went just after WoW: They expected 10 million players... and budgeted for that.
Apart from the fact I very much wish TR didn't go away, because I think it was fantastic, one of the things I got in the box was the OST and I think it's probably the best thing about the game.
Every area had its own unique music and it all fitted the mood of the area so well, it tried so hard to have an amazing atmosphere, only to be let down by the gameplay. When the game closed, they even made a special bit of music just for the last moments of the game.
Tracy Bush was the lead composer.