Part of the influx during Biden's presidency had to do with right wing media/pundits declaring that if Trump lost the election (2020) and Biden becomes POTUS, the borders would be wide open. Even to this day on these message boards, there are a number of people who claim the borders are wide open right now (because Dems are in charge).
That's not true, and has never been true. But the media needs to sensationalize things to compete and the media in Latin America pick up on this and repeat it. So now you have a huge group of desperate people who are hearing and reading that Democrats want/have instituted completely open borders, hence the influx among other factors.
It's purely hyperbole (borders are wide open, or Democrats want open borders).