In a zeitgeist characterized by technological underdevelopment and skepticism, Turing became a leader by suggesting computers could think:
Working from very little, he ushered science into a new era by bringing mechanical intelligence into the public eye for the first time, opening it up to enrichment, analysis, and criticism.
“Turing was definitely a leader; he created the absolute earliest examples of artificial intelligence. When one pioneers such an important concept, their role as a leader is obvious. Quite simply, he created a path for other intellectuals to follow. Since he introduced AI, the field has grown immensely, to the point where it’s fair to say all modern technology owes something to Turing.” 
The Oxford Dictionary describes a leader as “the most advanced or successful in a particular area.”  Weighed against scientists of his time, Turing was certainly the most successful in his attempts to define and construct intelligent machinery.