Speaking as a person who would, as part of $DAY_JOB, get back broken/burned/destroyed electronic equipment from the field, and then determine if it was to be junked or not, you've got some problems here.
First off: Fresh water or not, that's a lot of silt. And it likely got into everything electronic. And then things are going to go downhill from there. First, the bad news:
Silt contains things like salts (Yes, NaCl, but also every-other-positive-ion plus a-negative-ion known to man.) Most of these are hydroscopic; that is, given water vapor, they attract water molecules and form, well, a conductive slurry.
That conductive slurry means that dissimilar metals (copper, tin, zinc, iron, you name it) are going to trade ions back and forth and, well, corrode. We're not just talking the circuit boards, now: Individual components, be they resistors, capacitors, inductors, and all that jazz are going to be susceptible to this. So, if you were thinking that this beast of yours, after repair, might last, say, five years, you might want to think again.
Now, say one had something that got good and proper dunked in fresh water, sans mud. Well... that's not so bad. Water, as a rule, does have $RANDOM_JUNK dissolved in it, but, heck, circuit boards get washed with water.. albeit it, deionized water.
There's a heck of a lot of electronics in a Tesla. Computers, touch screens, you name it. I'm thinking about all that silt. IF you took every single blamed electronic control box out of there, washed the heck out of them with deionized water and really removed all residues, there might be a chance. But.. a coil, or transistor, with small spaces under the components and/or in the component, and you blasting away with a high-pressure spray, trying to get all that stuff out of the teensy tiny spaces and such.. Admittedly, any teeny tiny cracks that let teeny tiny silt particles in might let those teeny tiny particles back out again.. I'm sorry, I can't see where This Is Going To Work.
It gets stupider. My old Chief Petty Office in Electronics A school informed the class one say, "90% of your problems are going to be in the wires." He was dead right. So, think about all those connectors in the wiring harness. Not just in the mated ones, where there's rubber gaskets to keep moisture out, but on the other side of the connector. There's likely been silt & water intrusion in there, too. Urgle. I guess taking out all the wiring harnesses, left, right, and center, and blasting away to get all the salts in the silt out of the wires and connectors would be in order. OK: I know that Tesla's big on minimizing the amount of junk that goes into a car, but I'm a-thinking that we're talking at least a mile, and possibly as much as five miles, of wiring harness in that car. It'll all have to be cleaned.
I'm somewhat less worried, I guess, about stuff like the actual drive train, hoses, pipes, cooling systems, and that kind of thing. Probably because I'm a EE and ignorant of all that mechanical engineering stuff. But, as a EE, we work with things that are reactive: That is, metals. With the possible exception of gold nuggets, there's No Such Thing as Naked Metal in nature: Any such has been corroded to dirt over the eons and Nature, given a chance, will do that to stuff like copper and all those other metals I mentioned above.
I mean.. there are those scroll wheels in the steering wheel. Those are electric switches of some kind. The switches are in little plastic boxes that likely don't come apart. They're inside the passenger compartment where, well, large amounts of liquid weren't exactly expected, although I'll give you a splashed can of soda as a possibility. (The electrics in the wheels for ABS brake components and such probably are sealed aggressively against water intrusion.)
I really, really wish you hadn't tried turning the car on. With all that conductive slurry everywhere high voltage electronics literally got shorted out, hence the burning electronics smell. I suspect that the inverter electronics that chargers the battery are likely toast at this stage.
I guess.. Suppose you got one, maybe two Teslas of the correct vintage and type sitting in a junkyard after being totalled in some non-water related accident. You might then be able to mine that one or those two cars for dry components for your resurrection bid. But cars end up in junkyards like that so the junkyard owner can sell the parts as spares, so this might cost more than it's worth. Dunno.
I hate to throw a damper on your project, but do you really want to do this? If had been only fresh water, no silt, then I think you'd have a fighting chance. With all that silt, it may as well have been sitting in salt water.
