Python nested dictionary updating all dicts rather than specified

I am scraping results from a web table (link can be found in the code if needed) using BeautifulSoup. I then iterate through the table rows and subsequently iterate through the cells to produce a list of that row’s data. That list is indexed to pull out the name of a driver and their lap time which I want to add to a set of nested dictionaries.

However instead of just updating the values (two-levels down) for the dictionary I have specified (one-level down) it updates them for all the dictionaries.

My code (shortened and generalised the races and drivers):

#Imports
import requests
from bs4 import BeautifulSoup as bsoup

dataurls = {
    'race1': 'https://fiaresultsandstatistics.motorsportstats.com/results/2022-bahrain-grand-prix/classification/2c65d50d-606e-4988-81c5-7a4976ef0e6f'
}

#Setup the dictionary
races = ['race1', 'race2']
drivers = ['driver1', 'driver2']
mainDict = dict.fromkeys(races, {})

#Scraping elements
def webscraper(mDict, race):
    soup = bsoup(requests.get(dataurls[race]).content, "html.parser")
    #Dict for races, will contain driver key and lap time value.
    rDict = {}
    #Parse the table by row, extract driver name and lap time
    for tr in soup.find("table", class_="_2Q90P").find_all("tr", class_="_3AoAU"):
        row = ([td.text for td in tr.find_all('td')])
        dDriver = row[2]
        dTime = row[6]
        dDict = {dDriver: dTime}
        rDict.update(dDict)
    mDict[race].update(rDict)
webscraper(mainDict, races[0])
print(mainDict)

Expected output:

{
'race1': {'driver1': '1:30:100', 'driver2': '1:30.200'},
'race2': {}
}

Actual output:

{
'race1': {'driver1': '1:30:100', 'driver2': '1:30.200'}, 
'race2': {'driver1': '1:30:100', 'driver2': '1:30.200'}
}

I have tried so many different ways to get around it, the only other thing I can get to happen is that only the last drivers’ time is added to the correct race only.