Thalans are too keen on mining

There's something wrong with the Thalan AI. They always seem to build excessive amounts of space miners. At least twice I've been in a situation where everyone else has a decent army ready while Thalans had couple of dozen miners orbiting their planets and not a single military ship built

Games have been on a large map, tough, occasional asteroids and with 5 AI's so I can't see how even aggressive miner could want more than few miners.