Not sure why it’s so hard for some people to understand, aside from being a professional rider he also has a Youtube channel. He can still create content (as his job) for the channel regardless of what that content is, just so happens he wanted to spray his bike and document it for said channel (allowed) and he collaborated with another business that is still allowed to trade during lock down.
So Bren and Fat Creations engaged in a ‘business transaction’, no rules broken.
As for if/why/what masks they were wearing, why do you care? Concentrate on what you’re doing.