The way it works is that only teams that win the championship are guaranteed promotion. There are 4 times more leagues in div. V than in div. IV, so all those winners replace the 4 teams (2 automatically, 2 after relegation series) that get demoted in each div. IV league. The "extra" promotion of some teams happens to clean up bot teams that did not get relegated, and the ones that get promoted are the ones with the best regular season record which did not win the championship. In your case it means that all the bot teams replaced in div. IV made way for teams that won 22 or 21 games in div. V last season (the tie-breaker is the point differential).
the next best teams in your division will promote to fill in any Bot-controlled team spots in higher leagues