RationalWiki article on Craig.

[Jehanne]

He was able to get his country and his military to follow him down a path towards insanity, which had been laid in Germany by philosophers, scientists and economists within Germany and elsewhere in the West.  The Axis soldiers killed many more Allied soldiers than died under Hitler's command.  He got his country to believe in his crazy ideas and fight, kill and die for those ideas, which is the hallmark of a great leader.

If that is your definition of a great leader then Charles Manson is a great leader...  Leading your followers astray is the very definition of a bad leader.

I think the word you're looking for is charismatic.

"Great":

Definition of great

1. 1a :  notably large in size :  huge all creatures [i]great and small[/i]b :  of a kind characterized by relative largeness —used in plant and animal names the [i]great horned owl[/i]c :  elaborate, ample [i]great detail[/i]
   
2. 2a :  large in number or measure :  numerous [i]great multitudes[/i]b :  predominant the [i]great majority[/i]
   
3. 3 :  remarkable in magnitude, degree, or effectiveness [i]great bloodshed[/i]
   
4. 4 :  full of emotion [i]great with anger[/i]
   
5. 5a :  eminent, distinguished a [i]great poet[/i]b :  chief or preeminent over others —often used in titles Lord [i]Great Chamberlain[/i]c :  aristocratic, grand [i]great ladies[/i]
   
6. 6 :  long continued a [i]great while[/i]
   
7. 7 :  principal, main a reception in the [i]great hall[/i]
   
8. 8 :  more remote in a family relationship by a single generation than a specified relative [i]great-grandfather[/i]
   
9. 9 :  markedly superior in character or quality; especially :  noble [i]great of soul[/i]
   
10. 10a :  remarkably skilled [i]great at tennis[/i]b :  marked by enthusiasm :  keen [i]great on science fiction[/i]
    
11. 11 —used as a generalized term of approval had a [i]great time[/i] it was just [i]great[/i]
    

greatness
noun

https://www.merriam-webster.com/dictionary/great

I would say that I was referring to #3 -- "charismatic bloodshed" does not seem like a very expressive term to me. And, yes, Charles Manson was a "great leader", albeit, on a very small scale.