The key intuition here is that the decision about how many fireworks to provide for any individual is a function of the enjoyment that the individual gets from total fireworks, net of their cost. If a person gets a lot of enjoyment, or has a lot of money to finance the fireworks, he will choose to purchase more fireworks, even though he is sharing the benefits with others: as enjoyment net of costs gets very large for any one individual, the provision of the public good starts to approximate private good provision