Several things happened with Renault last year, mostly the screw up with lack of engines parts happened because they had so many failures in Mexico. The primary reason given was everyone calculates how much to turn down engine power due to lack of cooling and Renault screwed that up, turned their engines down less and everyone was basically stressing the engine all weekend.
Remember them telling Verstappen to slow down and he said along the lines of "I really can't go much slower". So one part is Renault had more comparative engine power because they screwed up and didn't turn power down as much as the other teams. Another major factor is... Verstappen was right on his game in terms of performance. Don't forget that he qualified well in Singapore, he pulled a lead on Hamilton in Malaysia with a pretty huge gap to Ricciardo. He had a iirc ~16 second to Ricciardo before Hams tires started to go in Japan which was clearly holding up Verstappen while Ricciardo in clean air only closed the gap to 10 seconds behind him. So Verstappen just had a huge amount of pace. Also iirc Renault bought their 2018 engine upgrades somewhere around Singapore, so they had a bump in engine power while Merc/Ferrari didn't bring as big a bump end of season so another kinda temporary closing of engine power helped Verstappen be that fast at that point of the season. Even in Cota don't forget Verstappen from 16th was fighting with Vettel and Kimi at the end of the race while Ricciardo, I can't quite recall, I think he had passed Bottas but wasn't keeping pace with the Ferrari's before his failure so again just Verstappen had pace that really no one but Hamilton could match.
I think people need to start to realise that Max is the real deal and is making a big difference in pushing the RBR forwards 10-15 seconds further up the track than Ricciardo can.
On the engines, turbo's don't really matter in terms of lost power, thinner air means the compressor has to work harder to get the same boost, meaning it can harvest less, which doesn't really work due to fuel efficiency and needing to finish the race so in reality, they drop engine power to maximise harvesting and reduce boost requirements. Also lack of actual cooling from thinner air also requires the engine to run less hard to achieve the same temps.
As for the track itself, does anyone see the track being a disaster in the rain? It's a track without a lot of grip and last year these cars had huge trouble just warming up the tires for a full lap with only Vettel and Verstappen managing to get good laps. Both Mercs, Ricciardo and Kimi without enough tire temp did comparably awful laps. A track that struggles to get heat into tires is going to be terrible in the wet is it not? I can see the narrow exit into the main straight catching so many people out in the wet, loads of people spun there in the dry already. If it's truly wet I can see a terrible race full of safety cars/red flags as people fly off it constantly.