Hartman, determined to eliminate the Martial God at the earliest opportunity, pushed a fleet operating in deep space into a planetary gravity well at all costs.
For the deep space fleet, the most critical attributes were "power of the main gun," "range," and "thrust." As long as the ratio of thrust to weight went up, then giant warships could intuitively fly faster than smaller spacecraft.
For the deep space fleet, "counteracting atmospheric drag and planetary gravity" were not necessary considerations. For the most part, only the planetary defense forces of solid planets and the aerospace fleet of gaseous planets needed to consider these factors.
"The military" is a highly specialized collective, with different parts having different functions and specializations.