omg. just
LOOLLL. Michael wore loafers and white socks since he was a kid. Check back through old photoshoots. It's what he wore when he was at home and obviously what he was most comfortable in. Hence why he wore it for years and years and it became a trademark look for him.
It was the fashion then. At least to Michael it was, because he idolised James Brown, Jackie Wilson and Sammy Davis Jr. The careers of all these guys kicked off guess when? In the 50s. When Grease is set. And all 3 men wore loafers or smart shoes with white socks. I think it's far far far far more likely MJ was thinking of his heroes James Brown or Jackie Wilson when he asked for his first pair of loafers (years before the movie Grease even came out).
Mr. James Brown
and his loafers
Mr. Jackie Wilson
and his loafers
Mr. Sammy Davis
and his loafers
Mr. Michael Jackson
and his loafers
5 years before Grease
6 years before Grease
Michael also wrote (in Moonwalk if I remember correctly, it's been a while since I read it) that his brothers use to tease him when they were kids because he would insist on wearing white socks with his shoes, when to them it looked old fashioned. But later on it became a trademark and kids all over the world would copy the look and Michael said he loved it because he liked to be a trendsetter.