You have to update the virtual app path or app base path in index.html to resolve this issue.
That is, the hosted application expects the assets from root folder of the web server. So, you have to update the subfolder name in index.html to serve the files from the path.
For example, if I am hosting the application in http://example.com/blazor/, the index.html looks like the following.
<base href="/blazor/" />
For more information, refer to the link for updating app-base-path.