From what I can tell, there are two major changes from Trump to Biden. First, Biden will not expel any unaccompanied child. I'm not a fan of illegal immigration, but I'm less a fan of not helping a child if you can, or at least not doing any harm to a child. Kid's cost money, but they're not really destroying the place. They go to a relative or foster care and become Americans in all things, but being legal citizens.
The second is that Biden seems to believe that anyone claiming asylum should be allowed to freely stay until an immigration judge decides on their status. But the problem is most of them don't qualify. They have crappy lives and want them to be better and are willing to work, and there may be dangers in their home country .... but they don't qualify for asylum. If Biden doesn't want to summarily expel them, even the ones who'd eventually qualify, I can see that because some qualified people probably get killed and tortured. BUT THEN why hasn't he doubled the number of judges? It's not a difficult job to qualify for. Any immigration lawyer can do it. The law is not complex.
So imo Biden is just in favor of letting people stay illegally.