The musicaly people were already veterans in Silicon Valley tech scene (not young under silicon valley standard & with years of working experience).

They raised money to build education product with short videos in it.

The education product was not doing well. So they cut everything and kept the short video part.

Sounds familiar?

YouTube was initially a dating website with videos. Then they cut the dating part and kept videos.

Instagram was initially a checkin app with photos. Then they cut the checkin part and kept photos.