Why are alternate repositories so hard to configure

I have the following

<repositories>
<repository>
<id>sonatype</id>
<name>Sonatype Maven OSS Repository</name>
<releases>
<enabled>true</enabled>
</releases>
<snapshots>
<enabled>true</enabled>
</snapshots>
<url>https://oss.sonatype.org/content/groups/public</url>
</repository>
</repositories>

But when I run maven I get

[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-site-plugin:3.3:site (default-site) on
project csharp-windows-elevate: Execution default-site of goal
org.apache.maven.plugins:maven-site-plugin:3.3:site failed: Plugin
org.apache.maven.plugins:maven-site-plugin:3.3 or one of its
dependencies could not be resolved: Could not find artifact
net.trajano.wagon:wagon-git:jar:1.0.1-SNAPSHOT in apache.snapshots
(http://repository.apache.org/snapshots) -> [Help 1]

/*Why in the world is it looking in
http://repository.apache.org/snapshots ???*/

So, then I configure nexus to mirror
https://oss.sonatype.org/content/groups/public and I add to my settings.xml

<mirrors>
<mirror>
<id>nexus</id>
<mirrorOf>*</mirrorOf>
<url>http://localhost:8081/nexus/content/groups/public</url>
</mirror>
</mirrors>

and then I get

[ERROR] Failed to execute goal
org.apache.maven.plugins:maven-site-plugin:3.3:site (default-site) on
project csharp-windows-elevate: Execution default-site of goal
org.apache.maven.plugins:maven-site-plugin:3.3:site failed: Plugin
org.apache.maven.plugins:maven-site-plugin:3.3 or one of its
dependencies could not be resolved: Could not find artifact
net.trajano.wagon:wagon-git:jar:1.0.1-SNAPSHOT in nexus
(http://localhost:8081/nexus/content/groups/public) -> [Help 1]

I know this to be a lie because when I go through the nexus UI I can
clearly see the artifact in question in both the nexus index and
storage. However, for some reason, the artifact pom.xml is neither in
the index nor storage. When I go to
https://oss.sonatype.org/content/groups/public/net/trajano/wagon/wagon-git/1.0.1-SNAPSHOT/
I can clearly see the pom.xml with the other files that nexus has
downloaded. /*Why is nexus refusing to download the pom.xml?*//*
*/
Cheers, Eric