In a simple statement: a better life.
We (the USA inhabitants (legal and illegal) have a better life than almost any other country in the world. Some of the European nations have a similar life but almost no room to expand.
The US has the physical room to absorb the migrants so many go un-noticed or they merge into existing population centers with barely a ripple in the general awareness.
This is the same think that drove the immigration from the 1180’s to the 1920’s. It is now far easier for the Latino community to move north through Central America and Mexico than at any other time. Huge sums of money are bering provided by varius governments and individuals to pay for the movement (See Glen Beck’s black bord presentation on YouTube).
It is easier and cheaper for the individual than at almost anytime.
Yes, I know the horror stories about the women and children and unfortunately they are tru. But, short of a strong military action on forgein soil there is not much we can do until they get to the border.
Restating my thesis: The USA is an economic heaven even at the worst of time and draws people from around the world, not just Latinos. That’s why they come.

Soros open border society ,.the deep state , NWO
Leftist demoncrap puppets RINO scum. The communist News Networks they are all paying for ,organizing , and are all putting American under attack.
This is the "UNCIVIL WAR"

Well there are about 60 million latino immigrants (and offspring) from the past 25 years, so its not exactly just starting to increase. The left has been encouraging anyone with no understanding of constitutional individual liberty and free markets to invade (illegally immigrate) and vote Democrat for decades- with the goal of destroying the republic and instituting socialism.
One explanation recently posted to the gulch by OUC: https://www.youtube.com/watch?v=GD7Xg...

Why the sudden surge in migration from Nicaragua, Honduras and El Salvador right now? It seems more like a cattle drive, but who are the drovers?

The "Red Scare" in the past resulted in the US supporting some very unsavory--but anti-communist--strong men, but something seems to have reached fruition now. What's going on?