That's because they were worse than the Nats.
Say what you want about Seattle as a baseball town, but when I went to Safeco last summer, the atmosphere at the park was way better than it's ever been at a Nats game, save for really special games (opening week 2005, opening night 2008, Strasmas, etc.)
The Yanks were in town and there were far more M's fans than Yanks fans, unlike when the Yanks came to RFK.