I have always wondered how spraying silicon etc onto electrical connections
makes them work. Apart from driving off water, one would expect it to cause
bad connections by it's insulating properties? (and I speak as an erstwhile
electronics engineer).
Auto connectors are usually not the best quality and have tin plated
contacts. They also often carry significant current and have voltage
drop across the contacts, so it only takes a little moisture to produce
electrolytic corrosion and the "white powder effect". The contacts slide
on mate and there's pressure between the surfaces. A thin film of silicon
spray forms a bubble around the mating surfaces, while at the same time
being easily penetrated by contact pressure to form a good contact.
Modern autos typically have dozens of connectors, many of which are
exposed and even if they are rubber sealed, this perishes over time to
let the damp in.
I tend to keep my cars for years, even decades, so I perhaps see more
of this sort of problem than others...