why do I need to configure both uploadArchives and artifactoryPublish for my build archives to be published?

Question

I have a lib.zip and myApp.war that I need to publish to artifactory. Initially, I started with artifactoryPublish, hoping that when I run ./gradlew clean release, the war and zip gets published to artifactory. But I observed only that the war gets uploaded. I had to add the include this additional to my build.gradle to get both zip and war upload

afterReleaseBuild.dependsOn uploadArchives. why do I need both?

If I remove afterReleaseBuild.dependsOn artifactoryPublish, nothing gets uploaded/published to artifactory.

Here is my build.gradle

buildscript {
    repositories {
        jcenter()
        mavenLocal()
    }
    dependencies {
        classpath "org.jfrog.buildinfo:build-info-extractor-gradle:+" 
        classpath 'net.researchgate:gradle-release:2.+'    
    }
}


allprojects {
    apply plugin: "com.jfrog.artifactory"   
    apply plugin: 'net.researchgate.release'

apply plugin: "java"
apply plugin: "maven"
apply plugin: "war"

group 'com.example.services'

sourceCompatibility = '1.7'
targetCompatibility = '1.7'

war {
    archiveName = "myApp.war"
}

task wrapper(type: Wrapper) {
    gradleVersion = '2.11'
}

task buildAssets(type: Zip) {

    baseName = 'lib'
    version = null
    from('libs/') {  
            include '**/*.jar'
}

assemble.dependsOn(buildAssets)

artifacts {
    archives buildAssets
}

release {
    git {
        requireBranch = '' 
    }
}

afterReleaseBuild.dependsOn uploadArchives
afterReleaseBuild.dependsOn artifactoryPublish

artifactory {
    contextUrl = "http://myartifatoryurl"
    publish {
        repository {
            repoKey = 'libs'
            maven = true
            username = "foo"
            password = "bar"
        }
        defaults {
            publishConfigs ('archives')
        }
    }
    resolve {
        repository {
            repoKey = 'releases'
            maven = true
            username = 'foo'
            password = 'bar'
        }
    }
}

//rest of dependencies here