Why does my child theme's enqueue of styles mess up the order of script enqueues from the main theme?

I have a child theme, generated:

function child_theme_enqueue_child_styles() {
    $parent_style = 'parent-style';
    wp_enqueue_style($parent_style, get_template_directory_uri() . '/style.css' );
    wp_enqueue_style(
        'child-style',
        get_stylesheet_directory_uri() . '/style.css',
        array( $parent_style ),
        wp_get_theme()->get('Version') );
}
add_action( 'wp_enqueue_scripts', 'child_theme_enqueue_child_styles');

But what happens, in my main theme, I also load bootstrap's CSS. If I am to enable my child theme, my bootstrap's CSS doesn't get overwritten by my style.css and as you can tell, a lot of visual bugs appear.

I need bootstrap to load before my style.css and it normally does, unless it's the child theme.

If I set a priority for this function above such as 9999, then it works again, it also makes sense why it works, but it doesn't make sense why it doesn't.

What's am I missing?