Laravel Save Many BelongsTo

public function update(UpdateCampaignRequest $request, $id)
    {       
        $campaign = Campaign::findOrFail($id);

        //A. Update all Regular Fields
        $campaign->update($request->all());

        //B. Update Terms

        // B.1. Delete all terms to write a new list
        $campaign->terms()->delete();

        // B.2. Assign the fresh terms list
        $myTerms = $request->input('myTerms');
        $myTerms = rtrim($myTerms, ',');
        $terms = explode(',', $myTerms);
        foreach($terms as $term){
            $term = strtolower($term);
            $new_term = Term::firstOrNew(['term' => $term]);
            $new_terms[] = $new_term;
        }
        $campaign->terms()->saveMany($new_terms);

        //dd($campaign);
        //$term = Term::create($request->all());

        return redirect()->route('admin.campaigns.index');
    }