You can't just spin up 6k new relays and take over the Tor network without somebody noticing. The network is actively monitored for sybil attacks, and it takes

You can't just spin up 6k new relays and take over the Tor network without somebody noticing. The network is actively monitored for sybil attacks, and it takes 2+ weeks before a new node is "trusted" with significant traffic, giving network monitors plenty of time to blacklist you. What's going to kill Tor is a global passive adversary, meaning someone with perfect visibility of all traffic going in and out of Tor nodes by tapping network infrastructure and correlating at the endpoints. I'm sure the NSA is working on this. They couldn't do it in 2013, but what could they have accomplished in the 6 years since the Snowden leaks? It's also possible to use machine learning to "fingerprint" encrypted blobs entering guard nodes and correlate them with websites (even onion services!), although it gets less feasible as the set of potential websites increases.