What I mean to say is that with a monorepo, you leave the door open to essentially passion-driven contributions made by the other half of that 2%. In non-monorepo environments, the barrier to uniform adoption is too high for someone that isn't full-time assigned to the task to justify.
Some people are genuinely passionate about this stuff, and want to take on the task of migrating the entire code base, because it's a fun challenge and it'll improve their day-to-day work every day for the remainder of their employment. They're very rare, but they do exist, and with a monorepo those people are better-equipped to drag the company forward.