They were probably U.S. citizens who can’t be kept from entering the country even during a lockdown.
Per Fedzilla in November...
Does this apply to U.S. citizens and lawful permanent residents?
This order does not apply to individual persons who should be excepted based on considerations of law enforcement, officer and public safety, humanitarian, or public health interests.
How did those folks get an exception...?
You’re probably right about the Canadian-Americans in the Pennsylvania covid family.
Canadian snowbirds have also figured out how to beat the system. They can legally fly to the U.S., but not drive here. So they load their cars up at the border and have them shipped across as cargo. Then they take a helicopter over the border, pick up their car, and are on their way to clogging the Florida freeways for the next several months.