Is failing to apply one's logic is the main cause of happening of ocd?

Not that simple: There are two main components of obessessive-compulsive disorder (a type of anxiety disorder): (1) intrusive and inappropriate thoughts, impulses, or images that cause a lot of anxiety or distress, and (2) repetitive behaviors (including mental "acts") that a person feels driven to perform in response to the obsession (or according to rigidly applied rules). There is even more to this diagnosis.

OCD is an anxiety: Disorder, often familial or seen in genetic syndromes (e.g., tourette's, williams'). Repetitive thoughts & fears recognized by the person with ocd as not reality-based (obsessions) lead to repetitive behaviors (compulsions), often unrelated to the obsessions, to reduce the anxiety temporarily. See a psychologist for cognitive-behavioral therapy & a psychiatrist for anti-anxiety medications.