I think that's actually where you will find the big difference in their respective career paths. For Rovanpera it made sense to make the step at the time. For Solberg it was a bit more complicated.
They both drove in Latvia as youngsters because they didn't have a licence. And as they began to beat people in Latvia started to add other championships. Rovanpera drove Latvia, Finland and Italy in 2017, Solberg did Latvia and America in 2019. They both did well at this stage, winning rallies and showing great speed and talent. Next step was WRC2 in 2018 for Rovanpera where he was fast but had some crashes, but he won a couple rallies, while Solberg was at a similar stage in 2020 racing in ERC and WRC2. Now this is perhaps the first point where Solberg lost a bit of momentum and experience because 2020 for him was to get used to being at the front in Rally2/R5 cars and it didn't help that it was a short year. The next stage for Rovanpera was full focus on WRC2 in 2019 where he won almost everything as we know, so far they had similar career steps and for Solberg this should have been 2021. But instead Adamo put him in the car on Arctic rally instead of the WRC2 as was the plan. After that he kept bouncing between the WRC2 and the WRC. Hyundai's Rally2 car was not great at the time so that plus constant switching probably confused him. Now at this point Rovanpera is a WRC2 winner having dominated the championship so Toyota decides to secure the future and put him in the car full time, the short 2020 wasn't good for him either but he had the WRC2 win behind him and he was steadily improving. Solberg got a partial season in a disorganised Hyundai team after a very confusing 2021.
I think Solberg is very talented but there was a big mistake made in his development especially when you put him side by side with Rovanpera's plan. I don't know who made the decisions of what to do, was it Adamo, the Koreans, his dad, Neuville, the Pope... In 2020 Oliver showed speed and 2021 should have been a year to focus on the WRC2 championship with some pressure and with fighting at the top but not so much to be in the main team, giving interviews etc. Most of the greats had that kind of season behind them when they went into the WRC and started to perform. That's Solberg's missing year.