A video i played on my apple phone had a siri command and my phones siri activated. What does this mean and what is a possible explanation?

A video on my friends iPhone 8 contained my friend asking Siri to play a song and his phone heard that and searched the song on safari and I'm quite confused and worried

It means you've discovered a curious quirk in the whole siri setup. An obvious one in retrospect, but also one that i doubt the developers foresaw. You should tell apple about it, maybe they'll fix it.

It is probably due to ḧey SIri hey siri is a feature on apple devices which if enabled you can bring up siri just by saying ¨hey siri¨. This feature is useful to bring up siri without having to do it manually

Your phone's "Hey Siri" feature heard the magic words and didn't consider where they came from. Nothing more.

Siri heard the audio cue from the video & acted accordingly. That's it.

That's the way Apple wants it.