I am not sure they can anymore, really. There have been a few MVP programs over the years.
- Tech Support/Customer Support. Those folks frequently provide help to other players with tech issues, common problems, navigating the Support system, answering policy questions, explaining services, explaining basic game functions, explaining Battlenet functions, etc. Those are selected by the lead of the TS/CS MVP program based on their long term forum contributions.
- Community MVPs. WoW, Starcraft, and Diablo 3 had Community forum MVPs selected by the Community Managers. The last round for WoW in 2018, they did take applications. They are people who are generally friendly and constructive on the forums. They are not game MVPs or something.
There are also a few specialized MVPs floating around such as the API forum, UI/Macros, etc. Those would have been selected for their long term work in those areas and willingness to help other players, such as the maker of DBM, a very popular group content raid/dungeon addon.
Those programs are pretty much mothballed now though. The shift to streams, youtube videos, etc is pretty large. That is where most of the “influencers” are now.
The WoW Community MVP program has not selected any members since 2018. The TS/CS program got the last MVP in 2019. D3 and SC have not had new MVPs in way way longer. Those programs are totally mothballed. I am the last of the D3 forum MVPs
You can read the official Blizzard Community MVP FAQ in the pinned welcome thread at the top of General Discussion. Scroll down until you get to the MVP part.
Most of the greens you see now, are TS/CS MVPs.