From what I see, proponents of Linux fail to admit it's shortcomings. To technologists some of these issues aren't, but to joe 6 pack, they certainly are. Multiple distros are a problem. Not that they exist, but in that they currently are missing 2 crucial things
Take Android. Consider each OEM to be a distro. It's the same situation as desktop Linux (roughly), why did it work where desktop Linux has failed? Unified branding, a unified store, and product on the shelf, as well as easily found online.
So step 1 is to get the major players together to promote Linux as a brand. Maybe they choose a different name, but it has to be unified. There also needs to be a store that follows that pattern. Joe 6 pack is likely to not fret very much over a distro, if the store is the same. Joe does not feel like he may make a choice that will cause him to not have the apps he wants.
Product on the shelf. This is the hard one. I don't have many answers. For online either. Problem is, even if you have a solid plan you need money to execute it. Speaking of this product, it has to be attractive. System 76 makes decent stuff, but by today's standards it's heavy and unattractive. There are a few of the big OEM's that have it preinstalled on good kit (XPS13), but they never really tell anyone, not like the 100 off win various win laptops every week, or the ads for them.