Renault and Red Bull Racing seem to depend on each other because of this rule
Renault might have to supply engines to Red Bull Racing in 2022. Whether Renault wants it or not, if no one else wants to supply Red Bull with an engine, Renault might be forced into it.
Honda stop
From 2022, Red Bull Racing will be without an engine. The team that won four world titles with Renault between 2010 and 2013 switched to Honda engines in 2019. The relationship had completely broken down towards the end and due to retirements in many races, Red Bull decided to take the gamble.
With Honda, Red Bull have recorded victories but the title is still out of reach. Now that Honda has already announced its departure from Formula 1 for 2022, a title chance in 2021 doesn't suddenly seem very realistic. How much will Honda need to improve? The focus was already on 2022, but now the question is with which engine.
Renault and Red Bull
This could turn out to be very difficult. Red Bull and Renault will not like to work together after everything that has been said about each other, but there may be nothing else. A new manufacturer doesn't get in so easily and if Ferrari and Mercedes don't want to supply an engine, Red Bull might be left without an option.
If none of the engine suppliers wants to supply an engine, FIA rules require the manufacturer with the fewest customers to supply the team. Mercedes will have three customers in 2021 and Ferrari two, whereas Renault has no customers. There is, therefore, a good chance that these two parties, whether they like it or not, are dependent on each other.
— Luke Smith (@LukeSmithF1) October 2, 2020