Uh, no. Your story doesn't hold up. Apple doesn't MAKE a car charger. Apple's stores sell Belkin car chargers.
It has to be a third party car charger and when a car is on, idling, the voltage can be higher then specifications if the device is just a plain resistance 12V to 5V DC voltage dropping device that many of the USB car chargers are. You can have as high as 16 volts in some cars. . . which means that what is being fed to the iPhone is actually 6 to 7 volts. . . with no amperage limiting circuitry. Great formula for a fire.
If you are referring to a cig plug, the the Lexus didn’t have one. The cable was plugged into the dash. I presume usb.
Is this the charger that you are referring to?
You’d think that Apple would verify compatibility if they sell something on their website?
https://www.apple.com/shop/product/HLRQ2ZM/A/belkin-usb-c-car-charger?fnode=97&fs=fh%3D458e%252B45d4
Especially if there are other factors involved - like a phone that has been dropped or otherwise subjected to damage...