How to add in previous comment text in Flask

I am using a fetch function in js to send to my server route in flask which looks this. I am trying to add back the previous comment in a bootstrap modal. The modal is opened when an edit link is clicked and for some reason, the request.form isn’t reading the target element where I am trying to put back the previous comment in the text area.

@app.route('/edit_comment/<commentID>', methods = ['POST'])
def edit_comment(commentID):
    user_comment = Comments.query.get(commentID)
    if request.method == "POST":
        user_comment.comment = request.form['comment_edit']
        return "success"
    request.form['form-control'] = user_comment.comment
    return "success"