Amazing. Seen it before in Bali but seeing it on youtube is extraordinary nevertheless.
Someone commented that it is an invention in the 1920s/30s by Westerners.
My response is:
真假假．假假真真．真亦假来．假亦真．What's real and what's false? The current version of the Hula Dance of Hawaii was invented too but it has since become a key identity of Hawaiian culture and tourism worldwide. The same goes for Kecak. The invented becomes real, and with time, it even becomes authentic.