Almost all of WhatsApp's 60 or so people were engineers at the time of the FB acquisition.
No. There is no way to build a billion dollar business without a management team. The founding team of a startup is a very significant part of the evaluation of any early-stage investor. Furthermore, regardless of the business of the app, there are critical business decisions and actions required of any business.
It doesn't mean that engineers can't fulfill the business roles and responsibilities (although at some point, this is likely the case), but it means that as a business grows, management responsibilities are required to run the company.
Somehow I think there's an underlying question within this question. Anyway back to your question, the answer is yes and no. It's possible to build a billion dollar business with a lean management team if the products you are selling are of high value, high demand, if the market is at the highest level of sophistication concerning your products e.t.c , you probably know this. At the very least, you as the business owner will need to manage business process, product creation, customer experience, the business' evolution e.t.c
It is however possible to build a multi-million dollar online business with little supervision thanks to the power of automation.
I sense an underlying need in your question, what do you really want to know. I am here to help. Give me a shout !!!
Also, just because a team was predominantly engineers doesn't mean they didn't have people that had responsibilities similar to what you'd call a manager.
Also, they're product was focused on one customers with one use case and that's not typical.