trash-event-after-expiration.php

<?php
/**
 * Description: Trash expired events automatically
 *
 * Usage: copy the snippet in your active (child) theme's functions.php file
 *
 * Plugins: The Events Calendar
 * Author: Modern Tribe
 * Last updated: February 19, 2019
 */

function tribe_trash_event_after_expiration(){
    if(is_admin()){
        return;
    }
    $args = ["end_date" => date("Y-m-d 23:59:59", strtotime("yesterday", current_time("timestamp"))), "posts_per_page" => 50];
    $events = tribe_get_events($args);
    foreach($events as $e){
        wp_trash_post($e->ID);
    }
}

add_action("init", "tribe_trash_event_after_expiration");