Elon Musk crossed the 100 million follower threshold on Twitter this week – a milestone that coincided with a rare bout of silence on the social network that has sparked speculation on Wall Street.

The billionaire Tesla CEO, who also turned 51 on Tuesday, became just the sixth Twitter user to amass 100 million followers and the first among prominent business leaders. Other accounts in the rarefied club belong to former President Barack Obama, Justin Bieber, Rihanna, Katy Perry and Cristiano Ronaldo.

Musk surpassed 100 million followers between Sunday and Monday, according to data from Social Blade. He has gained more than four million Twitter followers over the last 30 days alone.

Despite the major uptick in followers, Musk hasn’t posted on Twitter since June 21.

His tweets that day included a scathing response to a brewing FCC battle over broadband usage impacting his firm SpaceX’s Starlink satellite internet service, as well as a post responding to a Cars.com report that identified Tesla’s Model Y and Model 3 as the most “American-made” cars of 2022.

Musk also referenced surging gas prices by posting a year-old photo of a 7-Eleven gas station displaying a $7.11 price point during a sign test.

June 21 marked the publication of Musk’s most recent public media appearance – an interview with Bloomberg at the Qatar Economic Forum in which he warned of a likely US recession and identified key obstacles in his stalled bid to acquire Twitter in a $44 billion takeover deal.

The week-long silence is unusual for the billionaire, who uses his Twitter account to share everything from major updates about his businesses Tesla and SpaceX to irreverent memes to his fears about a potential population collapse.

As The Street noted, Musk’s Twitter absence occurred during a busy week in which the Supreme Court overturned Roe V. Wade and Congress passed a bipartisan gun safety bill in the wake of the deadly shooting at an elementary school in Uvalde, Texas.  

Musk’s absence also occurred as his Twitter takeover bid remains in a holding pattern. Twitter’s board unanimously voted last week to recommend that shareholders accept his $44 billion offer to buy the company.

The deal has been on hold since mid-May due to Musk’s lingering concerns about the number of spam bots within Twitter’s user base.

In his interview with Bloomberg, Musk noted that the spam bot issue is one of three remaining obstacles to the deal’s closure.

“Of course, there is the question of whether the debt portion of the round comes together and then, will the shareholders vote in favor? I think those are the three things that need to be resolved before the transaction can complete,” Musk added.