Probably these are the real owner of the accounts that make this claim and receive money back after they recognize to have been scammed.
Yes and the sender use hacked paypal/credit card info/bank account. There are many people who steal these types of information via classified ads.
Well not everyone is a scammer. Some people use pay pal like myself because they don’t have a bank account and that is all they have. I load mine with cash so maybe that’s why mine wasn’t reversible when I got scammed. I guess at the end of the day it all come down to trust. I have found people that will trAde bitcoin for pay pal. On Local.bitcoin.com people trade for pay pal but use a higher markup.