I'm developing a Wordpress plugin (integrated with WooCommerce) that fetches HTML Content from an API, and add it to a WP Post as post_content into an iframe, this way:

kses_remove_filters();
$newData['description'] = str_replace("\n", "", $newData['description']);
$newData['description'] = str_replace("\t", "", $newData['description']);
$post = $this->getPostByAPIId($product->api_id);

$id = $post->ID ?? get_post($product->woo_id)->ID;
if (isset($id) && !empty($id)) {
    $this->wpdb->update(
        "{$this->wpdb->prefix}posts",
        [
            'post_content'  => '<iframe class="custom-post" id="custom_product_post_content" src="' . htmlspecialchars('data:text/html,' . stripslashes(rawurlencode($newData['description']))) . '" style="display: block;width:100vw; height:100vh; border:none; margin:0; padding:0; overflow:hidden; z-index:999999; min-height:300px!important;"></iframe>'
        ],
        [
            'ID' => $id
        ]
    );
}
kses_init_filters();

Even if I put the kses_remove_filters(), when I open wordpress to check the new content, I find out that the post_content is empty.

If I try to debug the plugin with xdebug, I find out that post_content is updated, but when I refresh wordpress, the post_content disappear.

A few project specifications before starting:

1. I can't just embed the API as src
2. I don't want to fetch content via javascript
3. I used an iframe because I know that wordpress post_content can't embed a full HTML page like this: html > head { title } > body { style and various tags }
4. I don't write the HTML personally, I need to embed it via the API

Feel free to ask any question. Thanks in advance.