wp_editor metabox does not output the saved html format

Question

I have used wp_editor as a meta box for additional contents. Although it saves and displays the content, it does not save the format. Meaning, heading and paragraph tags are saved as simple text format. It ignores the HTML formats (heading, list, paragraphs) while saving.

Could anyone help me with some directions? I am stuck.

Thanks. I used the following code to register the metabox

class my_metaboxes{

    public function __construct() {
        add_action( 'add_meta_boxes', array( $this, 'my_overview_metabox' ) );
        add_action( 'save_post', array( $this, 'my_content_save' ) );
    }

    public function my_overview_metabox(){
        add_meta_box( 
            'page_overview_metabox', 
            'Page content overview', 
            array( $this,'content_overview_metabox' ), 
            'post', 
            'advanced', 
            'high' 
        );
    }

    public function content_overview_metabox( $post ) {
        wp_nonce_field( 'content_overview_save', 'content_overview_nonce' );
        $value = get_post_meta( $post->ID, '_post_content_key', true );

        echo '<input type="text" id="page_content_overview_metabox" name="page_content_overview_metabox" value="' . 
     esc_attr( $value ) . '" placeholder="Enter the page overview details" style="width: 100%; height:120px;">';

    }

    public function my_content_save( $post_id ){
       if ( ! isset($_POST['content_overview_nonce'])){
            return;
       }

       if ( ! wp_verify_nonce( $_POST['content_overview_nonce'], 'content_overview_save' ) ) {
            return;
       }

       if ( defined( 'DOING_AUTOSAVE' ) && DOING_AUTOSAVE ) {
            return;
       }

       if ( ! current_user_can( 'edit_post', $post_id ) ) {
            return;
       }

       if ( !isset( $_POST['page_content_overview_metabox'] ) ) {
            return;
       }

       $my_data = sanitize_text_field( $_POST['page_content_overview_metabox'] );
       update_post_meta( $post_id, '_post_content_key', $my_data );
       }
}

new my_metaboxes();