1. They didn't ban leaf blowers, the banned _gas_ leaf blowers. Electric ones are quieter, inexpensive, and work just as well nowadays. My building has an electric Milwaukee that was 200 bucks and lasts all afternoon on a battery or two.
2. This isn't about people wanting to manicure their lawns out in the burbs at 7am on Saturdays and using a gallon of gas per decade. DC is relatively dense with mid-rises and office buildings, it's the grounds crews and landscapers running them 9-5.
3. Coincidentally now with the age of work from home it's an extra boon not to have your neighboring building's super blasting a leaf blower below your window at 11am during your zoom meeting.
With any policy you have to look at the downsides -- people and companies have to buy new leaf blowers and batteries, what's the cost in money and environment? But I think they're fairly minor compared to the upsides in pollution and peace and quiet.
The main people who get hurt by this policy are small business landscapers, who are eligible for a subsidy to help replace equipment, which I think is a nice compromise.