I discuss this in my chapter-by-chapter essays: Prologue ACOK Stannis would not be a good king:
“…at this point in ACOK, Stannis would be a terrible king. Focused on his past to the exclusion of his present, on his personal injuries rather than the well-being of his subjects, inflexible and suspicious, a second King Maekar who himself ruled a brief time and died unhappily.”