It IS a front because if you openly state as the firm's mission and vision to summon a destroyer of worlds your business isn't going very far.
Aside from that, there are some things that dark cults need that just aren't cheap, nor easy to arrange.
For example, the summoning ritual may require the fresh blood of 600 healthy, young adult women. Try to imagine, for just a minute, the logistics involved in acquiring that without getting arrested. Just try.
Even if you are not going through the human trafficking route... A young adult woman will have around 4.5 to 5 liters of blood in her body. That fills 9 to 10 bags of donated blood. So you'll need about 6,000 bags of blood.
You can't just steal bags from a blood bank at gunpoint. Even if you don't get caught or shot, you would hardly be able to steal that much while keeping it fresh. Then you lose the bags with male blood. Then you lose the bags with blood from non-virgins. Then you lose the blood from the ones who were not healthy.
What you need is:
- A team of hackers that will break into blood bank databases and steal sensitive information;
- A team of investigators that will cross-examine data about individuals to find out which female donors are most likely virgins;
- A team of doctors and nurses to analyze the blood and separate useful blood from useless blood;
- A team of cons and white collar criminals that will defraud hospital records and other things in order to obtain blood bags in manners that seem legal;
- A team of people to transport the blood from hospitals/blood banks to the company's storagestorage;
- A team of lobbysts to convince the government on all levels - cities, states/provinces and country - to create sexual abstinence programs (masqueraded as STD prevention) so that you are statistically more likely to find virgin blood available in blood banks. And yes, government sponsored sexual abstinence programs are a thing in some places of the world.
And those are just the people who are going to be getting their hands dirty. You'll need managers to coordinate those people's efforts, human resources for recruiting, accountants for handling salaries, IT to develop the ERP system that is going to handle the data, a helpdesk department...
Now, you are unlikely to get all the blood you need in any single city, even if it is a metropolis like NY or Pequin. You'll need to go national at least. So you will need regional directors, and each branch will need another set of all the professionals above.
See, a corporation is not just something you'll use in order to get a nice place that is away from prying eyes. It is the minimum structure and organization that will be able to attain the materials you need for your rituals.