There's a long and rich tradition of scholarship on what constitutes a "good king" in medieval English history that is important (but missing) context for this article. Usually, scholars rate kings in terms of their effectiveness as rulers, rather than according to modern conceptions of morality in order to avoid anachronistically imposing a modern mindset on medieval rulers. So taking an English king and assessing his success and failures according to what his contemporaries would have considered success and failure. Often that consists of some version of these: maintaining a secure and prosperous realm, keeping fractious nobles and peasants in line, acquiring new lands for his followers, building up the church, screwing over the French and Scots, and securing a smooth succession after his death, ideally to his own male child.
The article's title (though less its content) challenges a common generalization about English kings: the more pious they were, they less effective they tended to be. A certain minimum of respect for Christianity was expected (e.g., when Henry II was forced to prostrate himself before the church to beg forgiveness for the murder of Thomas Becket), but on the other extreme, some notoriously ineffective monarchs devoted themselves to Christian worship to an extent that it undermined their ability to engage with the pragmatic, worldly concerns of ruling. Henry III and Henry VI, and to a lesser extent Edward II come to mind as the most obvious examples. Henry III and Edward II spent too much money and time building beautiful churches, neglecting the management of military and more pragmatic fiscal affairs. Henry VI was literally insane, and spent most of his time praying rather than ruling, which directly caused the first of the Wars of the Roses.
Sometimes Edward the Confessor gets lumped in with this crowd, because he was famed for his piety and he failed at the most essential task of any medieval English king: ensuring a smooth succession. Which in turn invited the Norman Conquest and thus the Harrying of the North and a near genocide of the Anglo-Saxon people Edward ruled (and failed to protect by not ensuring a smooth succession).
Ultimately, the generalization is probably flawed anyway (too few examples to identify a real trend, and too many confounding explanations like piety being an adaptation to severe mental illness), but this article does a bad job challenging even the lesser premise that the general rule applies to Edward the Confessor.