Making money in developer education is especially difficult. Especially if it isn't the specific core of what you are building. Surely there is plenty of education specific resources there, but it isn't as focused on it as Codecademy for example.

The last funding round closed in November 2018 at $30MM, which is a considerable sum - but it's been a year and a half since then and head count of 100-ish people does begin to accelerate the burn rate especially if the eyeballs and users haven't converted into paying customers.