These aren't really "pressing" questions. It's pretty simple. Top prospects change from year to year because there are either better players drafted or acquired, another prospect at the same position gets better, or the ex-top prospect has a bad season or two. The BP guys aren't psychics. Some players just don't pan out.
Broadway is still only 27, but trading a career minor league 1B can't be easy. We'd have to sell his pretty good power numbers and his solid OBP. But those numbers are on a lower level, so yeah, it'd be difficult.