Javascript CAML query javascript [Object Object]

I made a CAML query with the "CamlJS Console" Addon for Chrome. I joned 2 List to 1 relation list and my output from the query is always one item called "Kategorie" (category in english).

I want to write this into a field in the SharePoint newform.aspx, but the output i get is just Object Object.

I am not even sure if a join query is even possible through javascript because I am sure the query is valid.

At first: this is my caml query without using "include" :

<View><ViewFields><FieldRef Name='Kategorie' /></ViewFields><Joins><Join Type='INNER' ListAlias='cat'><Eq><FieldRef Name='KategorieID' RefType='ID' /><FieldRef Name='ID' List='cat' /></Eq></Join><Join Type='INNER' ListAlias='ctype'><Eq><FieldRef Name='ctypeID' RefType='ID' /><FieldRef Name='ID' List='ctype' /></Eq></Join></Joins><ProjectedFields><Field ShowField='Title' Type='Lookup' Name='Kategorie' List='cat' /><Field ShowField='Title' Type='Lookup' Name='Inhaltstyp' List='ctype' /></ProjectedFields><Query><Where><Contains><FieldRef Name='Inhaltstyp' /><Value Type='Text'>"+ contentTypeName.toString() +"</Value></Contains></Where></Query></View>

and this is the code built with the include:

var listItem = null;
var listItems1;
var listContentTypes = null;
var listItemEnumerator;
var oList;
var ctTypeID = undefined;
var contentTypeName;
var context;


function getContentTypeOfCurrentItem() {    

    listContentTypes = oList.get_contentTypes();
    context.load(listContentTypes);
    context.executeQueryAsync(Function.createDelegate(this, getContentTypeOfCurrentItemSucceeded), Function.createDelegate(this, onCtQueryFailed)); 
}



function getContentTypeOfCurrentItemSucceeded(sender, args) {    


    var ctid = ctTypeID.toString();
    var ct_enumerator = listContentTypes.getEnumerator();




    while (ct_enumerator.moveNext()) {

        var ct = ct_enumerator.get_current();   //durch enumerator designiertes element wird geladen

        if (ct.get_id().toString() == ctid) {

            contentTypeName = ct.get_name();    // read out Contenttype name 

            var list = context.get_web().get_lists().getByTitle("rel_cat_ci");
            var testQuery = new SP.CamlQuery();

            testQuery.set_viewXml("<View><Joins><Join Type='INNER' ListAlias='cat'><Eq><FieldRef Name='KategorieID' RefType='ID' /><FieldRef Name='ID' List='cat' /></Eq></Join><Join Type='INNER' ListAlias='ctype'><Eq><FieldRef Name='ctypeID' RefType='ID' /><FieldRef Name='ID' List='ctype' /></Eq></Join></Joins><ProjectedFields><Field ShowField='Title' Type='Lookup' Name='Kategorie' List='cat' /><Field ShowField='Title' Type='Lookup' Name='Inhaltstyp' List='ctype' /></ProjectedFields><Query><Where><Contains><FieldRef Name='Inhaltstyp' /><Value Type='Text'>"+ contentTypeName.toString() +"</Value></Contains></Where></Query></View>");


            listItems1 = list.getItems(testQuery);
            context.load(listItems1, "Include(Kategorie)");
            context.executeQueryAsync(Function.createDelegate(this, this.onRelQuerySucceeded), Function.createDelegate(this, this.onRelQueryFailed));  


        }
    }
}


function onCtQueryFailed(sender, args){

    alert("Query failed");

}


function onRelQuerySucceeded(sender, args) {
    var listItemInfo = "";                              //string for output
    listItemEnumerator = listItems1.getEnumerator();    //Indexed ref to queried elements

        while (listItemEnumerator.moveNext()) {
            var oListItem = listItemEnumerator.get_current();

            listItemInfo += oListItem.get_item("Kategorie");    
        }


    if(listItemInfo != ""){
        document.getElementById("cmdb_category_365755f2-3600-41d9-bf02-efb47430ebe6_$TextField").value = listItemInfo;
    }else{
        document.getElementById("cmdb_category_365755f2-3600-41d9-bf02-efb47430ebe6_$TextField").value = "Nicht Kategorisiert";
    }
}


function onRelQueryFailed(sender, args) {
    alert('Request failed.');
}



function getCtTypeListDefault() {   

    listContentTypes = oList.get_contentTypes();
    context.load(listContentTypes);
    context.executeQueryAsync(Function.createDelegate(this, getCtSuc), Function.createDelegate(this, getCtFail));

}


function getCtSuc() {   
    var ctTypeZero = listContentTypes.itemAt(0);
    document.getElementById("cmdb_category_365755f2-3600-41d9-bf02-efb47430ebe6_$TextField").value = ctTypeZero.get_name();
}


function getCtFail() {  
    alert("Something went really, really wrong! ContentType Liste nicht aufrufbar.");
}


function main(){


    context = new SP.ClientContext.get_current();
    oList = context.get_web().get_lists().getByTitle("cmdb_item");



    JSRequest.EnsureSetup();
    ctTypeID = JSRequest.QueryString["ContentTypeId"];

    if(ctTypeID != undefined){
        getContentTypeOfCurrentItem();
    }
    else{
        getCtTypeListDefault();
    }
}



SP.SOD.executeFunc('sp.js', 'SP.ClientContext', main)</code>