Republicans didn't go as hard on the border in the 1990s and 2000s as they did after Obama took office. I presume the experience of a black man being elected president made a lot of white reactionaries shortcircuit and they settled on the answer to "how did this happen" with "the democrats opened the border and flooded the country with mexicans / OTMs in order to cement their power"

I still wouldn't call Bush good on this, he definitely escalated the anti immigration rhetoric and created the model that every monster since him has followed