> And is a diesel truck supposed to be fuelling just one house? It's likely a single point of failure for a network of people

Completely correct, but then go one step further: Where does that truck fill up? At a depot where many other trucks do the same. That's an even more tempting target - centralised, stationary, flammable.

I do not think that there is an equivalent node in the solar alternative.

And where does that fuel depot get resupply from. etc. "decentralised" fossil fuel infrastructure isn't really a thing that exists.