Why are so many Americans in favor of illegal immigration and opposed to deportation?

The rhetoric and ideologies around illegal immigration seem to have taken a major shift in recent years, especially among the left.

Immigration was a bipartisan issue at one point in time, including under the Obama administration, with the common agreement being that those who enter the country illegally get deported. This is also the accepted norm and law of the land in many other countries around the world.

This seems to be a relatively new perspective for America. What caused this dramatic shift? And why are so many Americans opposed to mass deportations an in favor of undocumented immigration or support open borders altogether?