I am not running HomeKit or HomeBridge so this question would be better in the Hubitat HomeBridge Topic.
A quick primer is HomeKit is a Framework and runs on an Apple device (AppleTV for example) and vendors need to be Apple authorized (Hubitat for example) to play nice with that framework. Hubitat is currently in Beta attempting direct integration permission.
The HomeBridge solution runs on a device like a Raspberry Pi and is a 'workaround' to that integration authorization permission. The Hubitat HomeBridge application connects Hubitat to HomeBridge.
It is messy...and probably one of the very few reasons that Matter makes any sense.
Update:
I am an Apple household and workaround all the HomeKit stuff with SharpTools to build custom dashboards to integrate directly to both SmartThings and Hubitat and prevent all the hops.
