"... like a nuclear bomb went off" or a fuel-air bomb? If there was anyone to rule out as a suspect, I have to think it would be Pardo.
He had a murderous grudge against an area resident, a fuel-air device to test, familiarity with the area, and the requisite lack of regard for human life and the rights of others.
The fire was set (if it was set) when other fires were going on higher in the hills. There is speculation that the leaping flames in the hills might have "inspired" the mobile home park arson. If it were Pardo's flame thrower at work, perhaps is was less "inspiration" than a perfect cover to take revenge on his mother.
Investigators took note of the ferocity of the mobile home park, and noted its unusual intensity as a factor in the arson investigation. I have to think that investigators are now quietly investigating the possibility of Bruce Pardo's involvement in the Mobile home park blaze, if only to rule him out.