About Douglas, let's clarify some things, he is playing for A team since 2014 and was the best OH in WCH, putting him as starter it's not something from out of this planet.
Leal-Lucarelli it's not playing an entire cycle together, first Lucarelli skip it 2018 season, he was injured and Leal wasn't able to defend Brazil yet, and because in 2017 Lucarelli-Borges were the starters, so this Lucarelli-Leal duo who has played past two years actually happens during 2019 and VNL this year, since we all know 2020 didn't happen. So put Douglas as a starter it's not something based on change a system who has been stablished during 4 years, actually making him a starter it's more like going back to what we used to do.
Using Leal or Lucarelli over Douglas it's a tatic choice from Renan to have more fire power and just this. Going back to Rio 2016, we remember that Bernardinho started the games with Borges and then finish with Lipe, so change a player during the competition it's also not unusual.
I still thinking that Douglas fits better the Brazilian system who has been the same system since ages, especially now that we have a door instead of a libero.