Exposed headlight wiring harness

Heavens, those are crispy. No, there's nothing you can wrap those in that will bring them back to life.

You've had some thermal runaway right there. They have gotten hot over the years, just because headlights get hot. The terminals have gotten loose (repeated annealing because they get hot and cool off?) and corroded (accelerated by the heat) leading to worse quality of connection ... leading to more connection resistance ... leading to more heat, cycling back around to more of all of that.

Both connectors need to be replaced. If you had a Gen 3, I think all the headlight/foglight/etc. connectors are on a single wire harness that runs along the bumper and plugs in near the left wheel well, and you can find that whole harness online for not much and just replace the whole thing.

However, you have a Gen 1, and I think the headlight connectors are just part of the whole Engine Room Main wire harness, which sells for a tidy little sum.

So I doubt that's the way you'll be fixing it.

You can go to a Toyota dealer and pick up two of those plastic connector shells (part number 90980-11314) and six repair wires (three each) with splice sleeves and sealing material (the dealer parts counter can look up the repair wire and sleeve part numbers given the housing part number I just gave, or you can find them yourself in the wiring diagram at techinfo.toyota.com). The idea is to cut off all six wires a few inches back, where the good stuff is, and splice in the repair wires, which will already end in the right metal terminals that you'll assemble into the plastic housings.

That's the procedure that'll work for most connectors on a Toyota harness, but here you have an advantage because these connectors are for the headlights, and headlight connectors are really common.

You could pull in to any independent auto electric shop near you and they could do all of that in minutes, using connectors in their stock, and the proper crimp and sealing methods, and they wouldn't charge you much, and you'd have good headlight connections for another seventeen years.

You can also find the connectors on the shelves at Auto Zone or the like, and replace them yourself, but given how easy it is for your local auto electric shop to do it, and the importance of the right tools and techniques, I think DIYing it would probably be a false economy.