I assume you mean the Star Wars Half Marathon? Most people read “Marathon” as the one the first week of Jan, which is quite popular.
Personally, I wouldn’t adjust my plans on account of any runDisney event or crowd, you might not even know it’s going on. The races themselves are super early in the morning.
FWIW, the Star Wars Half isn’t even sold out yet.
They had it laid out in a way that the runners pretty much had blocked the entire area around Spaceship Earth. They ran in u-turned and ran out .... and they were holding guests back. They were rope dropping FEA. He grabbed his friends and they literally jumped in the race lanes right behind the end and followed them up to the turn, then jumped out and got ahead of most the rope drop guests.
Eep!
Disney cms have a method of letting people go through when it's safe for them *and the people who have been out on the course since 6am or so and are exhausted*. Let the cms do their jobs.