The phrase 'according to all that his father had done' seems straightforward, but it holds a subtle, and potentially dangerous, twist.
Inherited Faithfulness vs. Personal Faithfulness
While Uzziah followed his father's righteous path, this could imply a danger: simply mimicking actions without a personal commitment. True faith is never just inherited; it must be embraced and lived out by each person.
A Seed of Future Trouble
Although Uzziah is commended here, later in his reign (2 Chronicles 26:16-20), he overstepped his bounds by attempting to burn incense in the temple—a priestly duty. This suggests that even those who do 'right' can develop pride and stray from God's specific commands. His initial faithfulness didn't inoculate him against future rebellion.
This verse is a snapshot, a commendation at the start of his reign. It shows a foundation of doing good, but it doesn't tell the whole story of his life.