That article covers the broker services for MQTT but their real item is that many of the IoT devices that run a certain Wifi chip and vendor locked firmware can be re-flashed with Tasmota and thus opening a closed device to more services and support.
Once a device is reflashed you now have standard interfaces that supports MQTT, a WebUI, and HTTP commands that the Hubitat can integrate with. A lot of the hacking of these devices are well documented at the Home Assistant site since they seem to love to tweak devices.
I have been looking at all these Wifi connected "Alexa and Google Home" compliant devices and many are Tasmota supported and if you don't want to send all that control data to Amazon and Google flashing and then using MQTT to integrate makes some good sense.
