As I know (insider) players weren't satisfied with Kovač and his stuff and rebellion was led by Marouf
But it's hard to replace Julio Velasco. Players connected with him as he built them as a team, had authority because his achievements and Kovač came without any big result. I have really high opinion on Velasco, IMO he was Iranian the best player and what's the most important he knew how to manage Marouf and other stars. Lozano is on the same path or at least looks like that. I'm sure they'll look better and better, ticket to Rio is huge boost and Lozano proved he can manage this team.
Iran's biggest problem, in my opinion ofc, are OH's. Mirzajanpour isn't developing for 2 years (that's club fault not NT coaches), Ebadipour is oscilating a lot, Zarini should retire, Ghaemi is typicall defensive OH (except on serve). Manavinejand is a revelation as his offensive skills are great, as well as block but he might miss international experience.
On other side I'm not watching their quality through WL results for several reasons and can't make firm conclusions. WOQT was extremly exhausting tournament, both physically and mentally, and it's logical they didn't care much about WL. Mahmoudi was "squeezed" like a lemon and obviously tired. Same goes for Marouf and Ebadipour. Second reason, Ghaemi & Ghafour didn't play at all due injuries. Third reason is time. Lozano didn't have too much time to get players better, preparations for WOQT were improvised and Lozano used WL matches to check different tactics and how to play in various ways.
Matches in Rio will show their abilities and quality