The problem is not if Patreon is making enough profit to satisfy investors. The problem is if they don't. The reasoning goes as follows: VCs are chasing the next Google, and if Patreon cannot grow enough there is a real risk that it will die/resort to shady business practices by trying too desperately to achieve this growth. Without VCs it could remain a healthy, profitable, medium-sized company...
Exactly. It's the devil's bargain that you make when you take venture capital. VC is a hits-driven business. If it looks like you'll only be a moderate success, they will push you to take risks and spend more money in hopes of being giant. That will push up your odds of total failure and worse.