Create dictionary using JSON data

I have a JSON file that has movie data in it. I want to create a dictionary that has the movie title as the key and a count of how many actors are in that movie as the value. An example from the JSON file is below:

    {
        "title": "Marie Antoinette",
        "year": "2006",
        "genre": "Drama",
        "summary": "Based on Antonia Fraser's book about the ill-fated Archduchess of Austria and later Queen of France, 'Marie Antoinette' tells the story of the most misunderstood and abused woman in history, from her birth in Imperial Austria to her later life in France.",
        "country": "USA",

        "director": {
            "last_name": "Coppola",
            "first_name": "Sofia",
            "birth_date": "1971"
        },
        "actors": [
            {
                "first_name": "Kirsten",
                "last_name": "Dunst",
                "birth_date": "1982",
                "role": "Marie Antoinette"
            },
            {
                "first_name": "Jason",
                "last_name": "Schwartzman",
                "birth_date": "1980",
                "role": "Louis XVI"
            }
        ]
    }

I have the following but it's counting all of the actors from all of the movies instead of each movie and the number of actors per movie. I'm not sure how to do this correctly as I'm newer to Python so help would be great.

import json

def actor_count(json_data):
    with open("movies_db.json", 'r') as file:
        data = json.load(file)
        for t in data:
            title = [t['title'] for t in data]
            for element in data:
                for actor in element['actors']:
                    rolee = [actor['role'] for movie in data for actor in movie['actors']]
                    len_role = [len(role)]
            newD = dict(zip(title, len_role))
        print(newD)
                
json_data = open('movies_db.json')
actor_count(json_data)