Rule reminder
'Non tanto perché... quanto perché' (not so much because... but because / not as much because... as because) expresses a hierarchy of causes: it downplays one reason (introduced by 'non tanto perché') while emphasising another (introduced by 'quanto perché'). Both clauses take the INDICATIVE. The structure can also be used with nouns: 'non tanto per X quanto per Y'.
What does 'non tanto perché... quanto perché' express?