First, of course, he has only been indicted and not convicted. So technically it isn't for sure that he committed these crimes. Though, as you point out, the evidence is pretty damning.

I don't think the pandemic caused this...I think he's a very typical example of what's called a "civil reputable" family annihilator, like John List. He kept up the appearance of being a devoted family man, a successful businessman, but when that started to come crashing down, he decided to kill them rather than deal with it.

Though it is strange he only killed two of his children...I am extremely interested to hear what comes out at trial, to get the rest of the story.