AT&T T-mobile merger blocked by Department of Justice

So I'm not sure how I feel about this. I feel like this was a bad decision by the Department of Justice. Granted the AT&T T-Mobile merger would have made AT&T the largest mobile company in the U.S. but there are a whole team of other mobile companies large and small. I would understand an Anti-Trust suit if AT&T took out all of the competition but positioning themselves to become the largest from the third largest just seems like good business practice and not monopolization. Tell what you think.