How to save WYSIWYG content as post content

code.php

<?php
/**
 * This demo shows you how to save WYSIWYG field content created by Meta Box plugin as post content.
 *
 * @link https://metabox.io/docs/how-to-save-wysiwyg-content-as-post-content
 */

add_action( 'init', function () {
	// Remove the editor for the post type.
	remove_post_type_support( 'post', 'editor' ); // Change 'post' to your custom post type.
} );

add_filter( 'rwmb_meta_boxes', function ( $meta_boxes ) {
	// Get the current post content and set as the default value for the wysiwyg field.
	$default_content = '';
	$post_id         = filter_input( INPUT_GET, 'post', FILTER_SANITIZE_NUMBER_INT );
	if ( ! $post_id ) {
		$post_id = filter_input( INPUT_POST, 'post_ID', FILTER_SANITIZE_NUMBER_INT );
	}
	if ( $post_id ) {
		$default_content = get_post_field( 'post_content', $post_id );
	}

	$meta_boxes[] = [
		'title'      => 'Test',
		'post_types' => 'post', // Change 'post' to your custom post type.
		'fields'     => [
			// Register a wysiwyg field of which the content is saved as post content.
			[
				'type' => 'wysiwyg',
				'id'   => 'content', // This is the must!
				'name' => 'Fake content',
				'std'  => $default_content,
			],

			// This custom html is used to output custom style to overwrite the editor style set by WordPress.
			[
				'type' => 'custom_html',
				'std'  => '<style>#wp-content-editor-tools { background: none; padding-top: 0; }</style>',
			],
		],
	];

	return $meta_boxes;
} );

// Do not save to post meta.
add_filter( 'rwmb_content_value', '__return_empty_string' );