Maybe the organizations/persons who transported the migrants to the Mexican border expected a new group to provide transportation, food, shelter, sanitary facilities after the migrants crossed the border into Mexico. Maybe the extra day(s) at the border we’re not included in the money that the would-be invaders already paid.
https://www.breitbart.com/border/2018/10/19/watch-migrant-caravan-tears-down-border-fence-storms-mexico/
I don't see any *signs* that said "USA or bust"
just some foreign blue-striped flag of some sort ... BUT THEY ARE STILL COMING THIS WAY STILL CARRYING THEIR FOREIGN FLAG ...