It doesn't seem like the author of the original article knows what they are using the credit facility for, note the "maybe":

This new credit line means two things. First, DigitalOcean is sill investing heavily in its infrastructure. Maybe existing users will get a performance upgrade with new servers replacing existing servers. Or maybe DigitalOcean will expand its product offering.

And if they have to take out a credit line simply to upgrade existing customers, without bringing in new revenue, that is bad news. That means they are losing money simply to maintain their current position.