Re: geography, the Baltimore urbanized area has 2.2 million and is only 716 sq miles vs. 5.0 million and 1,322 sq miles for DC. As DC has grown it's stretched way out west to Leesburg. Baltimore not having grown gets rural 10-15 miles west of town past Ellicott City,and that 716 sq miles includes Columbia, MD. On top of that, metro DC permitted 6x as many houses and apartments last year than metro Baltimore.
It's more important for the Nats marketing efforts that they deepen support among the millions of people now living in Reston, Ashburn, Manassas, Stafford, Fredericksburg, Arlington, DC, Bethesda, etc, rather than battling for the thousands in border areas like Laurel and Columbia.
This MASN thing is temporary because cable TV is a dying medium for MLB and will account for a smaller share of revenues going forward. Long term, this DC welfare payment to Baltimore cannot make the latter a viable MLB market. It's not like the Orioles will ever get a share of the Nats gate, which is likely about 50-100% higher per fan than Baltimore's.