Multisite install in a subfolder won’t work with www

WordPress redirects to the URL you gave it when you set it up. So if you told WordPress you domain was www.domain.com and typed into the browser domain.com it would redirect to www.domain.com. This is expected. The only way to change that is to change it in the database. You can find the URL in two places in the _options table. Field names are home and site_url.