How Meta’s Muse AI Rally Helped Zuckerberg Pass Sergey Brin

Meta’s Muse launch gave investors a visible consumer-facing test of the company’s AI strategy. Strong early download data, a leading App Store ranking and a more optimistic analyst view helped fuel a sharp repricing of Meta stock. Because Mark Zuckerberg’s wealth is closely tied to Meta’s market value, that rally translated quickly into a very large paper gain—and later helped him move ahead of Google cofounder Sergey Brin in the Forbes wealth ranking. 616

The stock move came from AI optimism, not one app alone

Muse was reported to have reached 2.8 million downloads across the U.S. and Canadian app stores in its first 12 days, based on Sensor Tower data cited by Yahoo Finance. The same report said it set a U.S. daily-download record of 264,000 on September 19. 11

The app also overtook ChatGPT as the top free app on Apple’s U.S. App Store, according to market coverage. 4 That traction mattered because it gave investors a measurable sign of demand for Meta’s action-oriented personal-agent ambitions rather than only a longer-term promise about AI investment.

But it would be too strong to say Muse alone caused the rally. Forbes attributed the move to both investor confidence in the new autonomous assistant and Wells Fargo’s decision to raise its Meta price target to $796 from $640, while maintaining an overweight rating. 19

The key market figures

On Monday, September 21, Meta shares gained 11.3%, closing at $741.25. That one-day advance added about $192 billion to Meta’s market capitalization, according to Yahoo Finance reporting. 11

Other coverage put the closing gain at 11.4% and $741.24, a small difference consistent with rounding across market reports. 2 The broader September advance was also substantial: Investor’s Business Daily reported that Meta shares had risen more than 30% since the start of the month. 10

For investors, the important point was not merely the download count. The market was valuing a possible platform: an AI agent that could extend across Meta services and future devices.

How the rally changed Zuckerberg’s fortune

The wealth effect was mechanically tied to Meta’s share-price gain. Forbes estimated that Zuckerberg’s fortune increased by about $25 billion during the September 21 rally, reaching roughly $253.6 billion by mid-afternoon; earlier in the trading day, the estimated gain had been $12.9 billion. 6

A separate Forbes-based report calculated a $27.3 billion daily increase and a $255.4 billion net worth at its measurement point. 2 These differences do not necessarily indicate conflicting events: real-time billionaire rankings change with intraday market prices and the methodology of the tracker.

On the day of the initial surge, Forbes still listed Zuckerberg sixth as of 2 p.m. Eastern time. 6 By September 23, Forbes said he had overtaken Brin to become the world’s fifth-wealthiest person. 16 The practical chain was straightforward:

1. Muse’s adoption made Meta’s AI strategy more tangible to investors.
2. The enthusiasm coincided with a bullish analyst target revision.
3. Meta’s stock value rose sharply.
4. Zuckerberg’s estimated wealth rose with the value of his Meta holdings.

Meta Connect made Muse a device-and-infrastructure story

Meta Connect 2026, held after the market rally, showed why investors may have seen Muse as more than a standalone chatbot. Meta said it had added new Muse features, connectors and a new model, and that it would bring Muse to its glasses. The company also announced a broader AI-glasses lineup and Meta VR Glasses. 39

Meta’s product framing also included infrastructure for personal-agent tasks. Reporting from the event said Meta described a private, secure virtual machine for each Muse and said its Muse Spark model was trained specifically for personal-agent work. 36

That does not prove that Connect announcements themselves caused the September 21 price move. The evidence supports a narrower conclusion: early Muse demand, analyst optimism and expectations for Meta’s broader AI-and-wearables strategy combined to strengthen the investment narrative. The resulting share-price increase was what directly lifted Zuckerberg’s estimated wealth. 61939