Its due to a deeply embedded business philosophy where CEOs and other business people try to create bigger companies, and not necessarily better companies. Sometimes they are able to trigger a mushroom growth, but most of the times they fail. But due to survivor bias, they create a few more wannabe CEOs who again trey to create bigger and not better companies, and the cycle repeats.
Medium currently had a full fledged Sales, Support, HR and even a big ass operations dept. And 2 or 3 offices across United States. Their operations & other business depts were quite big in head count, even rivaling local oracle offices(which usually have about 1000+ employees). I can't necessarily say whether they had inefficiencies in their company structure, but they certainly over hired.
Even disheartening thing is that they might have already dried up most of their cash, and still don't know how to run a business. Executives are currently playing a dangerous game of "Let's see if we can raise more" and "We'll think of something".