Right after Obama was re-elected, he made a tour of Central America and Mexico, essentially selling them on his new DACA policy, encouraging policies to stimulate the immigrant flow, and bribing them with foreign aid. 2013 is when the child immigration really took off, and when the percentages from Central America took off.
It was a deliberate program of the Obama Administration, and the Left (in Central America and Soros groups).
My guess is that the Trump Administration has looked at what the incentives of the Central American Governments are, what specifically they can do to reduce the flow, and now they are applying leverage to them to do it. It is an important element of shutting down the flow.
One might say Obama did his white and black parts (sides) a screwgy??
Reminds me of the discussions in the 1980s, when American officials told South American countries they had to address their drug problems. They pointed out AMERICAN drug problems were fueling the trade - and in this case, American freebies.
IIRC, Obama had buses and planes ready to transport the DACA children and pretend children all over the USA. I don’t think that any were sent to Malibu or Nantucket.