There was a lot of charisma floating around, and I want to point that word back to its origin in describing spiritual gifts - I don't mean that people were necessarily tremendously likeable, gregarious, photogenic, gracious, good at putting others at ease or what have you. I mean that you would have the strong feeling of having met someone with a very distinct and often quite prickly sense of who they were in the world. Most people aren't like that: they might or might not have a robust private sense of identity, but either way they mostly prefer to rub along with others without standing out too much. Imagine wanting to be thought of as "intimidating"! If only so that you then have occasion to say to people "don't worry, I'm not intimidating really, what, little old me?", knowing full well that they find you very imposing, if not actually terrifying. But the source of that isn't pure narcissistic self-importance (although that can be a besetting vice), it's having gifts that you're not comfortable with and don't know how to control. If other people recognise you as different, even if you keep telling them that you don't want to be seen as different, then at least there is some confirmation that the thing that's wriggling around inside of you is real.
Mark was unquestionably very gifted, and by that I don't mean that he was some luminous once-in-a-generation genius, but he was too large for his own skin and kept having to find things to pour the excess out into. His teaching and lecturing were probably the most benign form this took; the dark magus stuff, not so much.
This will doubtless seem absurd in this particular connection, but I'm very fond of Susan Howatch's series of novels about Anglican priests who get derailed in one way or another by bits of themselves they don't fully recognise and can't control - sometimes their earthly, sensual nature (i.e. they end up shagging someone they shouldn't); sometimes forms of spiritual giftedness and insight which render them prone to dangerous pride (i.e. they try to fix complex emotional problems, and end up driving someone to madness or suicide). What you're supposed to do with such people is put them under the mentorship of a pretty stern spiritual advisor, ideally a monk with a colourful former life, who will tell them off if they start misleading themselves about who they are and what they're supposed to be doing. Well, it's a template for thinking about gifts and harms and how they sometimes come together. How do you guide someone who thinks they have a vocation, because they need to find a use for the thing that's wriggling around inside of them?