Governors command their states' National Guards, unless mobilized by the Congress or POTUS. Except in times of war or national emergency, a President must request the use of a state's National Guard. If a request is a "Request", a denial of the request is an option to the respective state's governor. IOW, Brandon did not command DeSantis.
DU-folk aren't the most informed of people, so here's a map of the US East Coast:
WashDC is at the Virginia-Maryland border. That means that more than 14 or 15 East Coast states are closer to WashDC than Florida (I included West Virginia in the count, and Maine would be #15 if it is closer than Florida). Obviously, there are also non-coastal states closer to WashDC than Florida.
More simply (because DU-onlurkers' minds wouldn't go there), there are more than 15 states whose National Guard units could get to WashDC more easily and quickly than Florida's. "Requesting" Florida National Guard units was an attempted hit on Florida's people and economy. DeSantis recognized it for what it was and chose to put up with political sniping - like DU's - rather than Brandon's political hit on his state.