The teens would not have had the knowledge (and probably not motivation) to acquire the stolen car without the TikTok challenge. The challenge was absolutely involved in the crash.
Edit: To add on to this a little - The challenge was probably not "Liable"; If I publish an article called "Here's how to rob someone!" I am probably not liable if you go out and rob someone. If I publish and article "Here's how to rob house 123 Main Street" and link you to it, there's probably a case for conspiracy. The tiktok challenge is probably closer to the former, but has some tinge of incitement. Either would be "Involvement".
Edit: To add on to this a little - The challenge was probably not "Liable"; If I publish an article called "Here's how to rob someone!" I am probably not liable if you go out and rob someone. If I publish and article "Here's how to rob house 123 Main Street" and link you to it, there's probably a case for conspiracy. The tiktok challenge is probably closer to the former, but has some tinge of incitement. Either would be "Involvement".