Whether she means to or not, Miss Havisham triggers Pip's undoing by encouraging a relationship between him and Estella. She puts her guided missile directly in his path, and it's a direct hit. If she had never summoned Pip to Satis House, Pip would never know to want to belong to the society she represents.
Pip may be our protagonist, but he's also his own worst enemy, rejecting those who love him most and choosing wealth over friendship. Luckily, his friends still love him.