Those folks committed suicide at the behest of the corrupt Mexican government. Nobody else is to blame.
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I'm gladd you asked. Here is the answer.
Get yourself a map of Mexico. You'll notice the roads and cities are in the southern third where there is water and low land. Much of Mexico is barely inhabitable barren wasteland. There is little industry and a teeming overpopulation growing by 2% per year even with massive migration out of the country. Fox needs to get rid of nearly 3,000,000 people per year to maintain the present state of chaos and poverty. They need to be moved North into the U. S. He also needs the industry in the state of California and similar places to furnish necessary jobs. Thus he needs to flood those areas with people and annex those areas. Without Aztlan Fox and Mexico are a cooked goose. Bush's kook agenda will facilitate Fox's plan.
He doesn't want ALL of them to come here (not the European types), but Mexico is a very racist country, their elites tend to be quite blond and the elites want the impovered Indians and Mestizos out or they fear they'll demand some changes and bring down their oligarchy which is how they obtain their vast wealth.