Order posts by meta value and Date

If you want both posts that have and do not have a meta key, you need an OR relation meta query to select both posts with key and those where it does not exist.

$args = array(
    'meta_query' => array(
        'relation' => 'OR',
        array(
            'key' => '_post_like_count',
            'compare' => 'EXISTS'
        ),
        array(
            'key' => '_post_like_count',
            'compare' => 'NOT EXISTS'
        )
    ),
    'orderby' => 'meta_value_num post_date',
    'order' => 'DESC'
);

$recent = new WP_Query( $args );