From the courtroom to the boardroom, it was a big week for tech investors.

The resolution of Google’s antitrust case led to sharp rallies for Alphabet and Apple. Broadcom shareholders cheered a new $10 billion customer. And Tesla’s stock was buoyed by a freshly proposed pay package for CEO Elon Musk.

Add it up, and the U.S. tech industry’s eight trillion-dollar companies gained a combined $420 billion in market cap this week, lifting their total value to $21 trillion, despite a slide in Nvidia shares.

Those companies now account for roughly 36% of the S&P 500, a proportion so great by historical standards that Howard Silverblatt, senior index analyst at S&P Dow Jones Indices, told CNBC by email, “there are no comparisons.”

There was a certain irony to this week’s gains.

Alphabet’s 9% jump on Wednesday was directly tied to the U.S. government effort to diminish the search giant’s market control, which was part of a years-long campaign to break up Big Tech. Since 2020, Google, Apple, Amazon and Meta have all been hit with antitrust allegations by the Department of Justice or Federal Trade Commission.

A year ago, Google lost to the DOJ, a result viewed by many as the most-significant antitrust decision for the tech industry since the case against Microsoft more than two decades earlier. But in the remedies ruling this week, U.S. District Judge Amit Mehta said Google won’t be forced to sell its Chrome browser despite its loss in court and instead handed down a more limited punishment, including a requirement to share search data with competitors.

The decision lifted Apple along with Alphabet, because the companies can stick with an arrangement that involves Google paying Apple billions of dollars per year to be the default search engine on iPhones. Alphabet rose more than 10% for the week and Apple added 3.2%, helping boost the Nasdaq 1.1%.

Analysts at Wedbush Securities wrote in a note after the decision that the ruling “removed a huge overhang” on Google’s stock and a “black cloud worry” that hung over Apple. Further, they said it clears the path for the companies to pursue a bigger artificial intelligence deal involving Gemini, Google’s AI models.

“This now lays the groundwork for Apple to continue its deal and ultimately likely double down on more AI related partnerships with Google Gemini down the road,” the analysts wrote.

Mehta explained that a major factor in his decision was the emergence of generative AI, which has become a much more competitive market than traditional search and has dramatically changed the market dynamics.

New players like OpenAI, Anthropic and Perplexity have altered Google’s dominance, Mehta said, noting that generative AI technologies “may yet prove to be game changers.”

On Friday, Alphabet investors shrugged off a separate antitrust matter out of Europe. The company was hit with a 2.95-billion-euro ($3.45 billion) fine from European Union regulators for anti-competitive practices in its advertising technology business.

While OpenAI was an indirect catalyst for Google and Apple this week, it was more directly tied to the huge rally in Broadcom’s stock.

Following Broadcom’s better-than-expected earnings report on Thursday, CEO Hock Tan told analysts that his chipmaker had secured a $10 billion contract with a new customer, which would be the company’s fourth large AI client.

Several analysts said the new customer is OpenAI, and the Financial Times reported on a partnership between the two companies.

Broadcom is the newest entrant into the trillion-dollar club, thanks to the company’s custom chips for AI, already used by Google, Meta and TikTok parent ByteDance. With Its 13% jump this week, the stock is now up 120% in the past year, lifting Broadcom’s market cap to around $1.6 trillion.

“The company is firing on all cylinders with clear line of sight for growth supported by significant backlog,” analysts at Barclays wrote in a note, maintaining their buy recommendation and lifting their price target on the stock.

For the other giant AI chipmaker, the past week wasn’t so good.

Nvidia shares fell more than 4% in the holiday-shortened week, the worst performance among the megacaps. There was no apparent negative news for Nvidia, but the stock has now dropped for four consecutive weeks.

Still, Nvidia remains the largest company by market cap, valued at over $4 trillion, with its stock up 56% in the past 12 months.

Microsoft also fell this week and is on an extended slide, dropping for five straight weeks. Shares are still up 21% over the last 12 months.

On the flipside, Tesla has been the laggard in the group. Shares of the electric vehicle maker are down 13% this year due to a multi-quarter sales slump that reflects rising competition from lower-cost Chinese manufacturers and an aging lineup of EVs.

But Tesla shares climbed 5% this week, sparked mostly by gains on Friday after the company said it wants investors to approve a pay plan for Musk that could be worth up to almost $1 trillion.

The payouts, split into 12 tranches, would require Tesla to see significant value appreciation, starting with the first award that won’t kick in until the company almost doubles its market cap to $2 trillion.

Tesla Chairwoman Robyn Denholm told CNBC’s Andrew Ross Sorkin the plan was designed to keep Musk, the world’s richest person, “motivated and focused on delivering for the company.”

WATCH: Tesla board chair on Elon Musk’s pay plan