The delete method only works when i delete the root node of a BST and I dont see the reason why.

    public boolean delete(int key){
        if(!search(key)) return false;
        root = helper(root,key);
        return true;
    }

    public BSTNode helper(BSTNode root,int key){
        if (root == null) return root;

        if(key < root.key){
            root.left = helper(root.left,key);
        }else if(key > root.key){
            root.right = helper(root.right,key);
        }else{
            if(root.left == null) return root.right;
            if(root.right == null) return root.left;

            BSTNode maxFinder = root.left;
            while(maxFinder.right != null){
                maxFinder = maxFinder.right;
            }
            root.key = maxFinder.key;
            root.left = deleteMax(root.left);
        }
        return root;
    }

    public BSTNode deleteMax(BSTNode root){
        if(root.right == null){
            return root.left;
        }
        root.right = deleteMax(root.right);
        return root;
    }

I have tried deleting leaf node, but it won’t delete anything other than the root node.