There's a couple things you can do to simplify and clarify this. If I'm following correctly, you want to update the Description and Short Description fields on the RITM, so let's start by confirming we can do that. Inactivate these 2 Business Rules and start simple, then you can tweak the results if it's getting triggered when you don't want it to. Start with one Business Rule on the sc_req_item table before Insert with no Filter Condition or Condition. The script is simply:
(function executeRule(current, previous /*null when async*/) {
current.short_description = current.variables.request_name;
current.description = current.variables.request_title;
})(current, previous);
or whatever makes sense with your variable names. Try this using the native UI first - submit the Catalog Item request form, then view the actual RITM record. You may notice on the order summary page after submitting the order, the Description is the Catalog Item Description, but then when you view the RITM record, the Description and Short Description reflect the variables. Once you confirm this is working, Portal is a whole different issue. Your widgets could be displaying the Description and/or Short Description of the REQ record instead of the RITM. So if it still looks wrong in Portal, you'll want the same one Business Rule since the RITM is created after the REQ, but you'll want to change the script to something more like what you initially tried, but you're going to lookup the REQ record, and save the changes with update():
(function executeRule(current, previous /*null when async*/) {
var gr= new GlideRecord("sc_request");
gr.addQuery('sys_id', current.request);
gr.query();
if (gr.next()) {
gr.short_description = current.variables.request_name;
gr.description = current.variables.request_title;
gr.update();
}
})(current, previous);
