There was no further explanation what may have caused the smoke and the glow, but it is safe to assume that this was not a standard feature of Apple's smartphone.
The carrier said that the flight attendant initiated "recovery actions immediately" and was able to "extinguish" the red glow "successfully". The iPhone was heavily damaged in the process. According to Regional Express, "the matter has been reported to the Australian Transport Safety Bureau (ATSB) as well as the Civil Aviation Safety Authority (CASA) for investigation and directions." The phone was handed over to the ATSB as well.
There was no information what may have caused the "smoke" and "red glow" and there were no related reports of similar incidents. However, we have heard of "iPhone fires" in the past, for example due to a defective USB ports.