I know the family pretty well and I've seen some inaccuracies here I wanted to try and clear up.
Josh ran 1:47.6i in HS for the national HS record. At that point, his training volume was not very high at all, particularly for a guy running that fast. The guy who previously held that record wound up at 1:44/3:34 in what I think we'd all agree was a bit of a disappointing career (no disrespect intended to him whatsoever). It isn't that much slower than what Josh has run thus far.
As far as coaching. He's never been "coached" by his Dad. His Dad has always been very hands on with Josh's career. As a result Josh has been through multiple coaches in multiple locations over the course of his career. Not the best type of environment for a promising prospect or for that matter an experienced runner. He was mismanaged, flat out.
The change to Rinaldi was huge for Josh. Justin spoke with a few different people prior to taking on Josh, including Josh himself and the level of comfort there was very high. The YT videos show Dad's involvement but this is nothing new. Rinaldi has mentioned (multiple times) in interviews that Dad plays a role trackside as does another Coach, but Rinaldi is developing the training and has done some things specifically for Josh.
The TLDR - His Dad made some REALLY bad tactical decisions early in his career. These absolutely set him back in his career and led to the lack of progress everyone witnessed first hand. The guy got with a coach that works well for him, dialed in the other elements of his training, and we finally saw the talent shine through. How he's upped the ante and spend the winter at altitude instead of in the PA cold and we're seeing another step forward.