Why can't the asset builder find
Answer to the Issue
The origin of the problem is when you ignore this: https://civicrm.org/blog/daved/action-required-drupal-8-installs-and-upgrades-composer-and-patches
To fix an existing installation which was upgraded or installed without the 'enable-patching' configuration, you can can do this:
composer config 'extra.enable-patching' true
composer update civicrm/civicrm-asset-plugin civicrm/civicrm-core civicrm/civicrm-drupal-8 civicrm/civicrm-packages  --with-dependencies


Original Post
I figured out that if you run
composer config 'extra.enable-patching' true

straight after
composer create-project ...

installation is going to work.
Background:
We have a scripted install which worked fine with 5.28.4 so I thought
to upgrade to 5.30.1 but got the following message at
cv upgrade:db

vendor/bin/cv upgrade:db
Found CiviCRM database version 5.28.4.
Found CiviCRM code version 5.30.1.
Checking pre-upgrade messages...
_Pre-announcement for upcoming version 5.30_: If your composer
configuration or composer.json does not enable patching, you MUST do that
BEFORE running composer to update your files to version 5.30. Either by
using `composer config 'extra.enable-patching' true`, or updating the top
level composer.json's extra section with `&quot;enable-patching&quot;: true`. See
Drupal 8 installation guide [1] for details.
The default copies of the message templates listed below will be updated to
handle new features or correct a problem. Your installation has customized
versions of these message templates, and you will need to apply the updates
manually after running this upgrade. Click here [2] for detailed
instructions. 

    * _Events - Registration Confirmation Invite_ - Support negative hours for
cancellation/transfer
    * _Events - Registration Confirmation and Receipt (on-line)_ - Support
negative hours for cancellation/transfer

The default copies of the message templates listed below will be updated to
handle new features or correct a problem. Your installation has customized
versions of these message templates, and you will need to apply the updates
manually after running this upgrade. Click here [2] for detailed
instructions. 

    * _Contributions - Invoice_ - Ensure that amount paid is shown even when
fully paid



Links:
------
[1] https://docs.civicrm.org/installation/en/latest/drupal8
[2] https://docs.civicrm.org/user/en/latest/email/message-templates/#modifying-system-workflow-message-templates

I hope that helps.