Adonijah's attempt to seize the throne was not a sudden impulse but the result of a deep-seated sense of entitlement. Three distinct factors fueled his supreme confidence and convinced him that the crown was rightfully his: his father's lenient parenting, his own striking appearance, and his status within the family.
The first factor was the way he was raised. Throughout his life, David never angered, shamed, or corrected Adonijah's behavior [רש״י, רד״ק, ביאור שטיינזלץ]. Because his father always remained silent, Adonijah naturally assumed that his actions were completely acceptable and even pleasing to David [מצודת דוד, אברבנאל]. This led him to calculate that if he were to declare himself king, his father would simply maintain his lifelong habit of silence [מלבי״ם, רד״ק]. Commentators offer different perspectives on why David never corrected his son. One view suggests that David simply avoided bringing up past mistakes, though he certainly would have intervened if he caught improper behavior as it was happening [צוארי שלל]. Another perspective argues that David was entirely unaware of the brewing rebellion, assuming Adonijah was merely displaying the natural, authoritative manners expected of a royal prince [אברבנאל]. Ultimately, withholding this crucial guidance proved fatal. By avoiding necessary criticism, David inadvertently paved the way for his son's destruction [רש״י, אברבנאל].
The second element driving his ambition was his physical appearance. Adonijah was incredibly handsome, which filled him with an inflated sense of self-confidence and the belief that he was naturally suited for leadership [מצודת דוד, ביאור שטיינזלץ, אברבנאל]. He recognized that a striking appearance wins the favor of the public and provides a significant political advantage [מלבי״ם]. His beauty directly mirrored that of his older brother Absalom. For both brothers, exceptional physical attractiveness bred pride and arrogance, which eventually erupted into open rebellion against their father [רש״י, רד״ק].
The final factor was his position within the family succession. The primary approach among commentators views this as a matter of legal right. Following the deaths of his three older brothers—Amnon, Daniel, and Absalom—Adonijah became the oldest surviving son. Consequently, he viewed himself as the natural and lawful heir to the throne. Beyond this historical reality, other traditions offer different ways to understand his connection to his older brother. Because the two brothers had different mothers, some suggest the link between them was a matter of upbringing. In this view, Adonijah was raised in the same flawed culture and with the same negative character traits that defined Absalom [רש״י, רלב״ג]. A more philosophical approach proposes that Adonijah believed his birth order actually worked to his spiritual advantage. He reasoned that because Absalom was born first, the older brother had absorbed all the family's negative traits and spiritual impurities, leaving Adonijah entirely pure, righteous, and uniquely worthy of the crown [אהבת יהונתן].