Elon Musk's relationship with the U.S. Securities and Exchange Commission (SEC) has been tumultuous, and several factors contribute to the ongoing scrutiny he faces:

1. Public Statements: Musk has been openly critical of the SEC. In a 2018 interview, he mentioned his lack of respect for the regulatory body, which has undoubtedly strained their relationship.

2. Past Settlements: In 2018, after Musk's tweets about taking Tesla private, he and the SEC reached settlements. Though he did not admit or deny the allegations, he had to step down as Tesla's chairman for three years and pay fines. Musk later indicated that he felt compelled to settle due to pressure from Tesla's investors and banks.

3. Twitter Activity: Musk's tweets, known for their candidness and unpredictability, have at times affected stock prices and investor sentiments, leading to allegations of market manipulation.

4. High Profile & Influence: Musk, being one of the world's wealthiest and most influential figures, is closely watched. His actions and statements can significantly impact markets, making any potential regulatory infractions more newsworthy.

5. Disruptive Influence: Musk's ventures, from Tesla to SpaceX, often challenge established industries. This disruptive stance can lead to increased scrutiny from various regulatory bodies.

6. Deviation from the Norm: Musk is known for not adhering to traditional corporate narratives. His outspoken nature and willingness to challenge the status quo might make regulatory bodies wary.

7. Advocate for Free Speech: Musk is a staunch advocate for freedom of speech. His commitment to this principle and his platform to voice opinions that might go against popular or established views can be a cause for concern for those who prefer a more controlled narrative.

8. Cannot be "Bought": There's a perception that Musk operates on his terms and cannot be easily influenced by external pressures, making him unpredictable in the eyes of regulators.

The SEC's actions against Musk likely stem from a combination of these factors, reflecting both his past behaviors and the broader challenges he poses to established norms and narratives.