A lot of information on how cars work is freely available online. There are plenty of videos, books, and courses that go over the mechanics of cars, it's fairly easy to educate yourself on a lot of topics these days, cars included. A lot of the devs are car people, too, who have worked on cars or have been around them extensively, so they probably know a thing or two about cars. Designing cars aesthetically, though, is a bit challenging. It doesn't require a degree, but it can be difficult to make a car look convincing and unique at the same time. This is an aspect that beamng does quite well (albeit with very few misses). There's a Japanese car magazine (MotorFan) that includes extensive writeups and interviews with some of the designers of cars like the Toyota Crown, Camry, Alphard, etc.. It includes sketches and clay models at various stages and does a good job at explaining the design process of cars. I highly recommend buying a few of them if you're more interested in designing cars.
both of those you have stated have 2 year gaps between release dates and its been 2 years since 2023 i bet we could get a new soliad this year
I'd imagine that's more of a cost and resources thing than anything. Some sound engineers could get the audio samples using microphones positioned in arrays around a vehicle. So let's say they wanted to get audio for the scintilla, they could use the V10 from the Gallardo or R8. Record intake, cabin, exhaust, and whatever. An audio tech works their magic, and now it's in game, but none of that is cheap or easy to do. Then there's the problem of the sheer number of vehicles, engines, and configs with different exhausts, intakes, and tunes. So they end up getting audio samples through some other means. Idk, I'm just talking - I'm way out of my depth when it comes to sound design....