To raise a material amount of debt, lenders generally require there to be collateralized physical assets against that debt. Compare that to equity financing which firms can use on literally anything (eg. marketing spend, hiring, etc).
So my guess is the $100M is going to go towards expanding their data centers in some way. We might see new regions from DO in the coming years or additional server types/services that run on top of those new servers.
The first part of your comment I’d say is accurate, but why would they have to spend a meaningful part of the $100 mil debt on infrastructure?
DO likely collateralized their existing infrastructure to get the $100 mil line of credit/debt, but will spend the $100 mil on other things in addition to some infrastructure (as the article suggested)
So my guess is the $100M is going to go towards expanding their data centers in some way. We might see new regions from DO in the coming years or additional server types/services that run on top of those new servers.