Is it very much normal for most MMOs to close/merge servers after the launch hype dies down. A lot of people don't stick around for very long.
But SWTOR is a special case, It was one of the most if not the most anticipated MMO ever. Literally EVERYONE was going to play SWTOR, and they did. Bioware had to open a lot of servers because of the very high population, but the game had some problems, clearly, so the populated dwindled and has continued to do so.