Some people leetcode for ages to get lucky in interviews. But loads of people just interviewed and are highly skilled and qualified. I think I did a week of prep ahead of my interviews.
Some people also get lucky. Luck is a huge factor in FAANG interviews. I've seen people who are definitely no more intelligent or better at LC type problems than average Joe just get lucky with their interview loops - while others who have won competitions just get the inverse luck and don't get an offer.
It's a numbers game overall.