I have a few problems with your theory...

You suggest that blowing on the cart adds moisture which increases conductivity. Sounds reasonable, yet why then does the game continue to keep working long after, even days and possibly weeks after the moisture has had to have evaporated completely?

The moisture in human breath would leave very little, a barely measurable layer of moisture. Were talking microns here... This evaporates in very little time and is hardly thick enough to increase any connection or conductivity. Your theory hinges on the idea that a impossible connection is made and mysteriously remains for hours, days, probably weeks long after the fact. This doesn't add up. You are imo, creating more NES myths...

Also you keep mentioning green mold... Have you ever considered this is most likely a patina?... This is after all a copper alloy right? You even brought up old coins somewhere...

Im gonna go with placebo. The original NES simply had too many design flaws. It is most likely the act of removing and reinserting that solved the issue be it dust, a weak pin connection or comm between the lockouts.

I do however agree, blowing on the carts isn't a good idea. But come on, Ive revived old carts that were Blockbuster rentals. Were not kids anymore and blowing on the carts is far less "abuse" than what we did to these things when we were kids. The fact that these things still work some 20 years later...