My one gripe with how Leo became the Leader in Rise was that it was just to sudden, Leo in 2012 became the leader of the team in a similar way but as Splinter had said later on in the series, he choose him because he knew since he was a child that he was destined to lead. Rise Splinter at the moment doesn’t seem to have any real reasoning for giving him the position, maybe though it’s because he was impressed with his performance back in the Battle Nexus that it made his view on him change from an irresponsible lazy teen to a competent strategic warrior?!
We’ll know when the movie releases this August.