Multi-Threading with selenium and Python Background processing

I currently trying to auto login into a website and fill a form.
I’m using selenium in python and am trying to multi thread each username in a different driver.

Issue is that drivers does open parallel to each other in the background yet they seem to not process the data unless they are opened in the foreground which does delay the process alot to wait for one to finish then process the next.

for confidentiality reasons I cannot share the website URL yet here is the code and functions used.

import undetected_chromedriver as uc
from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.support.ui import Select
from selenium.common.exceptions import NoSuchElementException,ElementClickInterceptedException,TimeoutException
from threading import Thread
import time
import pandas as pd 

Chrome options:-

chrome_options = webdriver.ChromeOptions()
chrome_options.add_argument('--no-sandbox')
chrome_options.add_argument('--headless')
chrome_options.add_argument('--enable-javascript')
chrome_options.add_argument('--disable-gpu')
user_agent = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/15.0 Safari/605.1.15'
chrome_options.add_argument('User-Agent={0}'.format(user_agent))
chrome_options.add_experimental_option("excludeSwitches", ["enable-automation"])
chrome_options.add_experimental_option('useAutomationExtension', True)

Functions used:-

def login_hbd(driver,username,password):
    WebDriverWait(driver, 20).until(EC.visibility_of_element_located((By.NAME,"username")))
    
    username_field = driver.find_element(By.NAME,"username")
    username_field.send_keys(username)

    password_field = driver.find_element(By.NAME,"password")
    password_field.send_keys(password)
    
    submit_btn = WebDriverWait(driver, 20).until(EC.element_to_be_clickable((By.ID, "submitBtn")))

    driver.execute_script("arguments[0].click();", submit_btn)
    
def get_ss_hbd(driver,username_list,password_list):
    while True:
        try:
            login_hbd(driver,str(username_list),password_list)
            WebDriverWait(driver, 1).until(EC.visibility_of_element_located((By.XPATH,"/html/body/div[1]/div/div/header/div/div[3]/nav/ul/li[7]/a")))
            driver.get("*****")
            driver.save_screenshot(f"{username_list}.png")         
            driver.close()
            break

        except (NoSuchElementException,ElementClickInterceptedException,TimeoutException):
            continue

Threading code:-

# get the start time
st = time.time()
number_of_threads = len(df)
threads = []

for _ in range(number_of_threads):
    username_list = df.loc[_][0]
    password_list = df.loc[_][1]
    driver = uc.Chrome(chrome_options=chrome_options,service_args=['--quiet'])
    driver.get("****")
    t = Thread(target=get_ss_hbd, args=(driver,username_list,password_list)) 
    t.start()
    threads.append(t)

for t in threads:
    t.join()
et = time.time()

# get the execution time
elapsed_time = et - st
print('Execution time:', elapsed_time, 'seconds')