We've got some baseball references coming up. We never considered having Earth conquerored, but we did press the studio for the longest continuing arc possible. They would only go for six episodes, but to be fair, we felt that was enough and were happy to have six shows off the station. The Dominion War will still continue, however, throughout the rest of the season. It is the most valuable thing in the alpha quadrant.
Space is Big.
The War is Big. We assume that Starfleet has many committments in many places and can't be everywhere at once. There's probably a fleet stationed not too far away from Bajor at this point. We felt that the Prophets' intervention made sense in the overall context of the series. After all, the pilot introduced Sisko to the Prophets and his journey from a man who didn't believe in them to a man asking them to behave like gods was a story that has always felt important to the series.