I have that too sometimes, videos in my recommendations that were watched by people or channels I subscribe to.
Also when I watch Min Chan Kim drone vids I get all kind of korean stuff, or when I watched Tareq Alsaadi it's arabian stuff.
Youtube can get a bit creepy sometimes, for instance when I've got some medical issue, and suddenly I get videos for that without searching for it.
Not even searched on Google or anywhere and Youtube manages to come up with the right medical selfhelp video for that problem.