REST API return encoded Multiline Textfield but show it correctly

I save a JSON string in my SharePoint list.
This looks like:

{"columns":[{"name":"A","visible":true,"width":200,"sort":{},"filters":[{}],"pinned":"left"},{"name":"B","visible":false,"width":150,"sort":{},"filters":[{}],"pinned":""},{"name":"C","visible":true,"width":200,"sort":{},"filters":[{}],"pinned":""},{"name":"D","visible":true,"width":200,"sort":{},"filters":[{}],"pinned":""}],"scrollFocus":{},"selection":[],"grouping":{},"treeView":{}}

But if I request it from the SharePoint I get:

{
  "d": {
    "results": [
      {
        "__metadata": {
          "id": "Web/Lists(guid'78e7e9bc-d85f-4c18-8aeb-213a68b28154')/Items(1)",
          "uri": "http://sharepoint2013/sites/acme/demo/_api/Web/Lists(guid'78e7e9bc-d85f-4c18-8aeb-213a68b28154')/Items(1)",
          "etag": ""1"",
          "type": "SP.Data.SettingsListItem"
        },
        "Configuration": "<div class="ExternalClass41AB4CF73C1C4DCB82C4F0B8CCCBC7AE">{&quot;columns&quot;:[{&quot;name&quot;:&quot;A&quot;,&quot;visible&quot;:true,&quot;width&quot;:200,&quot;sort&quot;:{},&quot;filters&quot;:[{}],&quot;pinned&quot;:&quot;left&quot;},{&quot;name&quot;:&quot;B&quot;,&quot;visible&quot;:false,&quot;width&quot;:150,&quot;sort&quot;:{},&quot;filters&quot;:[{}],&quot;pinned&quot;:&quot;&quot;},{&quot;name&quot;:&quot;C&quot;,&quot;visible&quot;:true,&quot;width&quot;:200,&quot;sort&quot;:{},&quot;filters&quot;:[{}],&quot;pinned&quot;:&quot;&quot;},{&quot;name&quot;:&quot;D&quot;,&quot;visible&quot;:true,&quot;width&quot;:200,&quot;sort&quot;:{},&quot;filters&quot;:[{}],&quot;pinned&quot;:&quot;&quot;}],&quot;scrollFocus&quot;:{},&quot;selection&quot;:[],&quot;grouping&quot;:{},&quot;treeView&quot;:{}}</div>"
      }
    ]
  }
}

So why? The SharePoint show it correct… So why the REST API must encode it? -.-

Thank you in Advance for any ideas!