Could you expand on that a bit?

Sure!

Democrats used to be far more conservative on immigration than they are today - both among the rank and file and in party policy, as the following links show in varying ways:

X (Twitter): Matthew Yglesias on X: "Notable that on immigration the divide among rank-and-file partisans is much more democrats moving left than Republicans moving right."
theatlantic.com - The democrats immigration mistake
fivethirtyeight.com - How democrats became stuck on immigration

There are lots of reasons for that, but a mostly right explanation is that rising influence of latinos and college-educated progressives (which are not mutually exclusive) within the party caused a massive shift in how the coalition deals with immigration generally, and undocumented immigration specifically. So in the past, policies that once had some support (though not universally) within the Democratic coalition, like stringent workplace enforcement and swift deportation of border crossers, are more broadly condemned as having cruel and inhumane impacts on marginalized immigrant communities. The rank and file went from being just about indistinguishable from Republicans in terms of whether immigrants were a benefit to the country to being full-throated in support of immigration....while GOP attitudes remained generally static.

Part of the reason that was able to happen is that the status quo worked. The system is broken, but in a way that is more acceptable to more people than any specific alternative set-up:

nytimes.com - Economy illegal immigration

Mass relocation of asylum applicants changes that. Big blue states are getting hit with impacts that make the status quo untenable. It's all well and good to talk about addressing the root causes of migration, but none of those causes can be addressed on a time scale relevant to the problem (if they can be addressed at all by the U.S., since we don't have control over many of those factors).

If this keeps up, it may force a shift in what the party is willing to support in terms of immigration enforcement.