I doubt they need to crack it (but they probably will eventually if they haven't already). There's plenty of ways to get around encryption with enough resources. No doubt they could gain access to root certificates and encryption keys if they wanted to. Not to mention exploiting backdoors in different equipment or performing MITM attacks on encrypted traffic. Once quantum computing rolls around all our current encryption will be completely worthless anyway (
so much so that the NSA is worried about it too).
I meant illegal activity pertaining to Tor's usage. Don't go buying drugs, guns, stolen credentials, etc. Don't go trying to hire a hitman. Don't go looking for CP or other disgusting material, etc. Abide by country specific laws too; if the use of anonymity software is illegal in X country and by using said software you face the possibility of imprisonment, injury or death then I definitely don't advocate doing so.
Tor's better for privacy but nowhere near as user friendly as a VPN. I attempted to use Tor as my main browser after the Snowden leaks and it was a miserable experience.
If you're happy to deal with all the issues that come with using Tor then feel free to use it. I personally only use it via Tails when I desire actual anonymity and the rest of the time I keep a VPN permanently connected.