If the videos showed it in real time, not compressed, it wouldn’t look anywhere near as “simultaneous.”
One big weatherfront with lightning will start fires over a broad area as it passes, fires which would appear simultaneous in a video edited for time.
There can also be a delay effect, where a front starts a number of fires that stay very small until the air dries and a good wind comes up, at which point fires will take off over a wide area in a very short time. This can happen even a couple of days after the storm.