It seems to me that their lack of stuff indicates that they are being supported by others in a coordinated effort - an invasion.
As you have mentioned the various Catholic churches, etc. But even a bunch of relief organizations would need some lead time in getting ready for this I would think The cartels is an interesting possibility. Or perhaps Soros? The promise of a bunch of cash at the end of the journey, and the promise of support along the way means you don’t have to worry about it yourself.
Heh - they’re getting a free ride to a free ride.