Straight but gay porn

I always and exclusively prefer women in my walking life and love girl on girl porn. But a few times a year i randomly get a hardcore urge and spend a weekend on a gay porn marathon. It gets me so hard and I jerk off like seven times a night during those splurges and I spend all day thinking about it. But after 2 - 3 days this goes away COMPLETELY and it does nothing for me and it's back to vaginasIs this just human nature or why does this happen