هَذَا وَجَدْنَا السَّلَفَ
We found the early predecessors adhering to this position.
Salaf refers here to early authoritative generations and their inherited scholarly practice. Their predominant position is evidence for the established Sunni ranking, but reports of unanimity must be distinguished from reports of qualified disagreement.
Where early scholars differed or suspended judgment over ʿUthmān and ʿAlī, it would be inaccurate to erase that qualification while describing the generally accepted order.