Was told my surgery for diverticulitis made scarring which caused narrowing of anal canal. Can this narrowing also be a common cause of diverticultis?

Do you MEAN anal?? Surgery for diverticulitis does not involve the anus, and anal narrowing is not a complication of diverticulitis surgery. The area where the colon is re-attached can become narrowed for several reasons. These are very different things- please clarify your concern for a more meaningful answer.
No. The out-pocketings that set you up for diverticulitis are mainly diet related. Low fiber diet can predispose you to the condition. Constipation can aggravate it. Sadly, intestinal surgery often leads to scarring and strictures. Let your surgeon manage the narrowing. If you're not happy with their suggestions, get a second opinion.