Details from the video's description:
Here we have a P-38 dropping a pair of 110 gallon napalm tanks on a row of planes, with a few other vehicles present. The length of the streams of fire running along the ground depends largely on the tank capacity, which in the game varies from 55 gal to 175 gal. And so the length of fire here is roughly midway between the shortest and longest possible. The speed of the tanks also plays a role, with higher drop speed resulting in longer streams.
In addition to the fire streams running along the ground, larger animated fireballs slowly rise convectively, transitioning into dark smoke. There is a random occurrence of none or several ballistic fires arcing away from the mess, trailing smoke. Remaining on the ground are a number of smaller fires scattered along the ground track, disappearing after a longer time. There may be also be an accompanying smoke column which lasts as long as those fires.
This one effect involves 8 discrete elements, each being a separate effect. That's not counting the effects for the destroyed vehicles, of course.
Note that soon after the planes/vehicles have been destroyed, one of them exhibits a secondary explosion. I have implemented such random secondaries for lots of object types, the chance of occurrence varying from type to type. And a few different secondary explosion effects are used, with some randomness in their selection where appropriate. This is but one area in which much more variety and randomness is incorporated, resulting in a much less predictable set of events. Gone are the days of the very same, limited effect for every event involving a particular object type.