• Leo KoGuan is a major Tesla shareholder and regularly touts his big buying sprees of the stock.

• But the one-time, self-proclaimed Elon Musk "fanboy" has since soured on his leadership.

• "Elon abandoned Tesla and Tesla has no working CEO," KoGuan tweeted in December 2022. "Tesla needs and deserves to have working full time CEO."

Leo KoGuan is perhaps best known as an Elon Musk "fanboy," who built a massive stake in Tesla during the pandemic and consistently fires off tweetstorms about the EV maker.

As of January 2023, was was also sitting on a net worth of $3.8 billion according to Forbes, and dumped the majority of his other stocks to amass more than 22 million shares of Tesla.

But while KoGuan remains "stupidly loyal" to Tesla and continues to buy up shares, he has recently soured on Musk, who has turned his attention to Twitter after taking it over last year.

"Elon abandoned Tesla and Tesla has no working CEO," KoGuan Tweeted on December 14, 2022. "Tesla needs and deserves to have working full time CEO."

He didn't respond to Insider's requests for comment.

KoGuan, 67, was born in Indonesian, went to school in the US, and now lives in Singapore. He is the chairman and founder of the IT provider SHI International, which touts clients like AT&T and Boeing among a list of 20,000.

He started the firm in 1989 after graduating from New York Law School in 1985 and earning a masters degree in international affairs from Columbia University in 1982. SHI began as a software reseller, and the New Jersey-based company is now one of the largest privately held firms in the US, according to Forbes. SHI had $14.3 billion in sales last year, up from more than $12.1 billion in 2021.

KoGuan has stepped away from SHI's day-to-day operations, with ex-wife Shai Lee in the role of CEO. He is now more focused on philanthropy — and Tesla.

He once met Musk at SpaceX's headquarters in 2019 and told Forbes in 2021 that he's "Elon's fanboy." In fact, he's the third-largest individual shareholder of Tesla behind Musk and Oracle founder Larry Ellison, according to Bloomberg's Billionaires Index.

And even as shares have plummeted 70% from their highs, KoGuan is still buying. But in recent months, he has dismissed some Musk fans as cult followers and expressed some buyer's remorse.

He took to Twitter on January 7 and said he thought Musk was "killing" both the company and shareholders, adding that he wouldn't have invested in the company had he known Musk would sell so much of his own stock.