Valve Took the Correct Approach with the Artifact Leak

Valve's upcoming Digital Trading Card Game ("TCG"), Artifact, suffered a recent setback when a Chinese Streamer streamed video from Artifact's closed beta. For those interested, the video can be found Here.
Artifact is based on the popular Dota 2 game, which has one of the largest esports scenes in the world (and has actually paid out the most money to its competitors of any esport). As a result, expectations are high for Artifact. The game is currently still in closed beta, and the closed beta players are participating under an Non-disclosure Agreement ("NDA"). Simply put, this means that as a pre-condition for access to the beta, the players had to "sign" (likely digitally) an agreement not to show any closed beta gameplay or discuss the confidential Artifact intellectual property outside the group of closed beta players.
Valve has been immensely successful in maintaining this confidentiality up until this most recent leak. There are very few closed beta tests that don't eventually have a major leak of assets and information. As Valve opens up the beta test to more participants (the game releases on November 28) the likelihood of a leak rises.
The basic facts surrounding this leak are as follows: a Dota 2 professional, Newbee's Xu "Moogy" Han, had access to the Artifact beta under an NDA. Moogy allowed one of the assistant coaches for Newbee, Lu "Rubick" Renfei, to play on his account. This simple act was already likely a violation of the NDA, but what Rubick did with the account once he had access was a flying leap over the line of permissible content. Rubick streamed Artifact gameplay for approximately an hour, which showcased cards that had not yet been "spoiled" (shown) to the general public.
Valve has been engaged in a social media campaign publicly showcasing Artifact cards and mechanics as the release date approaches. This has generally consisted of posts on Twitter, and by giving card assets to members of the competitive card game community to show to the outside world for the first time. This strategy has been seen by most as a resounding success. It is not a new strategy, Magic the Gathering has been following a similar strategy for its expansions for years, but it has definitely raised interest in the game by utilizing a slow, controlled trickle of information. The Rubick leak, by showing over a dozen of hereto-not-released cards threatened to put a damper on the hype.
Valve would have been well within their rights to react strongly to the leak. Moogy, by allowing Rubrick to play on his account and stream to the world, had clearly violated the NDA that he had agreed to honor when he was selected to playtest Artifact. An NDA is a contractual agreement, and Moogy had violated it.
Valve's owner Gabe Newell is notorious for public spats when he disagrees with how people involved with his projects behave ("James is an ass, and we won't be working with him again."). So I was interested to see how Artifact would handle this incident. It looks like they've learned from their earlier attempts.
First, Newbee took action by firing Rubicksfrom his Assistant Coach position on the Newbee Dota 2 team. This is a big deal--this was Rubick's job. Newbee also put out a public statement explaining the facts of the situation (that Rubick, not Moogy, was the author of the stream).
Valve could have turned Moogy into a public example. Moogy has earned over a million dollars playing Dota 2, and Valve controls all the strings to the Dota 2 Pro Circuit. Valve likely would have been well within its rights to suspend or ban Moogy from all their intellectual products, including Dota 2.
Instead, Valve made the smart decision. They quietly revoked Moogy's beta access, and have yet to make a public statement about the incident. The closest post that could be seen public acknowledgement of the leak is SirActionSlacks, a public personality who works closely with Valve on Dota 2 and Artifact, stating that the leak was the equivalent of burning down your house.
Valve has continued along its normal social media strategy of showcasing a slow and steady stream of cards, including those cards that were leaked by Rubick. Judging from the reaction on Twitter, where most of the cards have been showcased, most casual viewers are completely unaware of the leak.
By refusing to give the leak story oxygen by taking drastic public action, Valve has effectively mitigated the harm caused by the leak. This is a classic situation where the ability to take legal action does not correlate with the reasonableness of actually taking said legal action. Legal action is often a "burn down the house" strategy. It is also usually a negative-sum action from a public relations standpoint. It is an attorney's job as a legal "counselor" to advise when the benefits of taking further action are outweighed by the risks, and I believe that Valve took the correct approach here to bury the situation by refusing to make a big deal out of it.
Of course, it could just be that the leak just wasn't a big deal, and Valve were just not that concerned. It's impossible to say without an inside source, and as we move closer to Artifact release day the answer to the question is becoming less and less relevant. Valve knows they have a game that is likely to be a huge commercial success, with or without any closed beta leaks, and nothing will slow down the hypetrain.