main thread stops when I declare new thread in python code example

Example 1: threading python example

# A minimal threading example with function calls
import threading
import time

def loop1_10():
    for i in range(1, 11):
        time.sleep(1)
        print(i)

threading.Thread(target=loop1_10).start()

# A minimal threading example with an object
import threading
import time


class MyThread(threading.Thread):
    def run(self):                                         # Default called function with mythread.start()
        print("{} started!".format(self.getName()))        # "Thread-x started!"
        time.sleep(1)                                      # Pretend to work for a second
        print("{} finished!".format(self.getName()))       # "Thread-x finished!"

def main():
    for x in range(4):                                     # Four times...
        mythread = MyThread(name = "Thread-{}".format(x))  # ...Instantiate a thread and pass a unique ID to it
        mythread.start()                                   # ...Start the thread, run method will be invoked
        time.sleep(.9)                                     # ...Wait 0.9 seconds before starting another

if __name__ == '__main__':
    main()

Example 2: threading python

import threading
import time

def thread_function(name):
     print(f"Thread {name}: starting")
     time.sleep(2)
     print(f"Thread {name}: finishing")
 
my_thread = threading.Thread(target=thread_function, args=(1,))
my_thread.start()
time.sleep(1)
my_second_thread = threading.Thread(target=thread_function, args=(2,))
my_second_thread.start()
my_second_thread.join() # Wait until thread finishes to exit