There's a lot to take in here, but Nonprofit Quarterly has produced an amazing graphic that shows what drives the U.S. nonprofit economy. Those of us in the charity nonprofit sector are so involved in fundraising from donors, foundations and corporations, we often forget that those only make up about 1/6th of the total revenue that flows into American nonprofits.
One thing worth noting - Donor Advised Funds (DAFs)are giving more to nonprofits and receiving a lot more scrutiny. In this study based on 2015 data they made $15 billion in contributions. That was less than corporations. Flash forward to 2020 and DAFs gave nearly $50 billion - 2 1/2 times the corporate amount.