When I was younger somehow my yt search history contained porn but I never once searched for it...

Yeah so it used to happen 4 years ago... I was 13 back then I'm 17 now and the glitch stopped happening after a few months.... It doesn't happen anymore but I'm just curious as to why it happened in the first place.... No one in my family had access to the account.... Idk why tf would anyone search porn on yt in the first place.... I checked multiple times no one had access to the gmail account I was using... So yeah does anyone have a clue abt what actually happened to am I taking this mystery to my grave?