Yes, of course everyone knows this. But it’s true for successful breastfeeding too. According to one study (Clinical Pediatrics, Vol. 33, No. 4, 214-219 (1994)):

Strong approval of breastfeeding by the father was associated with a high incidence of breastfeeding (98.1 %), compared to only 26.9% breastfeeding when the father was indifferent to feeding choice

Fathers’ strong approval tripled breastfeeding rates. Wow.