That supplies power from the alternator to everything when the engine is running. If there are a lot of electrical items running at the same time and/or the battery is recharging at high rate, any weak spote in that line can overheat.
Redfish, on here, has written about it. That connector was added "at some point" (year) to make it easier for factory to connect engine to bay. Older cars don't have it, and it is a BIG failure point
Every connection can be a source of resistance. They are more exposed to heat, moisture, vibration. The crimp can have mechanical failure or weakness, reduced contact area, and the terminal contacts themselves are often somewhat thin and sometimes, not as much surface in contact as the wire conductor itself.
Based on Redfish's observations, its as likely the failure was due to normal heavy use as it may have been to abuse.
The easiest way to abuse the main circuits is charge a nearly dead battery by driving around on the highways.
