I found 4 or 5 incidents of pilots deliberately flying aircraft with passengers into the ground over 30 years. I haven't tried to figure out how many fatal accidents there've been amongst airlines during the same period, but I know it's way, way more that that. Pilot suicide causes a tiny proportion of what is already a tiny number.
I'll say it again.
There are very few instances of airliners being lost in the cruise with no immediately apparent cause. Of those, the instances of suspected deliberate pilot action form a significant fraction.
There is no
statistical argument against it being a possible cause in this case.