I've always wondered, in such cases where you have an open core and plan to monetize on extra features and plugins; what do you do if the community just goes ahead and adds those extra features? Or someone forks the project and adds the features?
It's extremely difficult for most enterprise customers to donate to FOSS projects. Small donations just aren't part of the normal corporate decision-making process. Very few people within an organisation have the authority to just give away money. Spending relatively small amounts of money on products and services is an utterly mundane part of doing business. If you maintain a FOSS project and don't offer an "enterprise license" of some description, you're leaving money on the table.
It's likely the maintainer is in the best position to start a company about the product to deliver more features faster and at higher quality along with more inherent trust.
Natural moats are rare and highly sought after and fought for, and is actually much harder to build than a typical business based on product value.