Met similar problem in Flask project. In my case, raw HTML tags were transfer to HTML entities, for example, “< p >” is transfer to “&ltp&gt”, thus the setData did not consider them as HTML tags.
I think you should check the source code of your web page, and to see what is in the setData().

For Flask, the following answer solved my problem:
Passing HTML to template using Flask/Jinja2

I am currently using ckeditor in my Django project.

setData() in inserting the text as raw html content. Any suggestion how to convert that raw HTML to rich text when setData() us used.

Follwing command is used by me.

CKEDITOR.instances.editor1.setData( "<%- data.description %>" );