why do people use them for a singular person sometimes? (not because they are non-binary)

why do people sometimes use ''them'' on english for a girl/boy?? i mean like B.person is an girl/boy and near to the end of the sentence A.person uses ''them'' for B.person(im not talking about she/they-he/they pronouns btw)

example:

İ like Micheal jacksons songs, i have every album of Micheal jackson, and i always listen to them

why did the A.person used ''them'' for the B.person (which is Micheal jackson in this sentence)