Imagine if a televangelist somehow managed to amass a devoted global following and used the funds from the offerings he gained from them to turn his cult into an N.G.O. superpower. How exactly would he be able to achieve that position and how would he keep it that way with or without actually possessing supernatural powers?
You are speaking of a church.
The catholic church, for example, are an NGO superpower. They are ruled by a single individual and his close circle of advisors. They have a high financial turnover and are in fact one of the richest organisations on this planet.
If you look at sects like the Mormons, Bhagwan, or Scientology, you can see how individuals and/or small groups of people can create a belief that is attractive enough for large numbers of people to join and spread internationally. An advantage is that religion is protected under the laws of many countries.
Oops, just noticed that this answer was already given in a comment to the question. Didn't mean to steal that idea...
Your televangelist needs to be so much more than just a shouty-doomsayer - build a cult of personality around them, with more than just "religion" at the core of their brand, such that people will want to be like them, or to support them.
They need to be a skilled Rhetorician, with an engaging or interesting personality, present some sort of mass-marketable skill (such as writing & performing amazingly popular music?) and espouse a deceptively simple and hard to disagree with Creed / Message, with a subtle twist or "stinger" to make it more popular by allowing people to enjoy following it. (e.g. "Be Excellent to each other" and "Party on, Dude"?)
It took the Catholic Church several hundred years to build themselves up. With modern technology, the message will spread much more quickly. Like Chronicidal said, the main part of this theocratic megacorporation would lie with the televangelist themself. Some key traits:
- Charisma - People would have to be drawn to them.
- Inner Circle - A small group of close supporters to help spread the message and provide/leak insights to the televangelist's history and personality.
- Supportive Spouse & Family - Part of the Inner Circle, but loss of a spouse/child adds weight to the message, and it's usually easier for blood heirs to carry the legacy. Also, the spouse can take care of "worldly matters" to free up the evangelist's mind/time.
- Poverty - Either born into poverty or as part of a "lost it all" period in their life, especially useful if part of the message includes "health & wealth.*
- Military Service - While a lack of service isn't necessarily a detractor, a term of service in the military is usually viewed positively, even more so among older generations. They could avoid some moral quandaries by being a medic or other support-type personnel.
- A Minor Scandal - Nothing so serious that their career would be ruined. Just serious enough to show they're "only human" and to give the Spouse/Inner Circle a chance to show their support and dedication to the cause.