He was witty, worrying aloud about the safety of a bush when a slip-sliding journalist reached out to steady himself. He was revealing, rolling up his jeans to show off a new coffee-cup tattoo on his ankle. He was sweating in his gray Puerto Rican scholarship fund T-shirt, but he turned on the charm — embracing farmers, thanking donors, listening attentively to discussion of fungus infestation and seed regulation.

And he was relentlessly on message: Puerto Rico needs help.

“A year ago, this island changed forever,” he said at the small family-owned coffee farm in Jayuya. “We’re going to have their backs.”

“Hamilton” has given him both resources — he’s making millions of dollars a year — and renown — access to princes and presidents, magazine covers and movie deals.

Mr. Miranda’s philanthropy, which he conducts in collaboration with his family, is still taking shape but is growing fast. Over the last two years, the Mirandas have given more than $4.6 million to nonprofits and have raised another $8 million, after expenses, through sweepstakes campaigns for a variety of causes, according to Sara Elisa Miller, the family’s director of philanthropy.

Their interests are varied, including developing artists of color; encouraging political involvement by Latinos; and supporting voting rights, immigrants, women’s health and education. And in the wake of Hurricane Maria, which killed about 3,000 people and caused damage to the island’s infrastructure and economy, they have been especially focused on helping Puerto Rico.

“It needs help, and it needs attention,” Mr. Miranda said, “and one of the weird side effects of ‘Hamilton’ is this megaphone that I didn’t really know what to do with in the beginning.”

That megaphone means that Mr. Miranda is a signal booster, able to use his visibility and his huge social media following to call attention to issues and causes. After the hurricane, the Mirandas helped raised $43 million for the Hispanic Federation’s hurricane relief fund — an effort that was inadvertently boosted when Mr. Miranda, in an uncharacteristic outburst, said on Twitter that President Trump would go to hell for criticizing the San Juan mayor — and also helped with a toy drive that delivered 40,000 Three Kings’ Day gifts to Puerto Rican children.