You can't think of any, because you're incredibly stupid. Here are some:
- Biden halted border wall construction
- Biden ended the "Remain in Mexico" policy,
- Biden put a temporary halt on deportations
- Once he was deporting again, he limited it to people who were imminent threats
- Dems talked about a path to citizenship after 8 years (not enacted, but still a pull factor)
- Created an iPhone app so that large numbers of people could automatically schedule appointments and then just cross the border and wait for a hearing
- The influx of so many people across the border offered ample cover for criminals to slide in among the crowd while border agents were overwhelmed
Additionally, in several Democratic-led cities and states, local governments provided
- emergency housing
- sanctuary status
- financial aid
- cell phones
- healthcare access
- legal services
- and allowed illegals to vote locally
... more "pull" factors.
The Dems took many steps to make it far easier, safer and more rewarding for border crossings. It was like "Border Disneyland" when Biden was POTUS.