I don't know in what contexts you read the different uses on the Internet, but as a general suggestion, DON"T use the Internet as a place to learn correct grammar.
The correct use is:
They make it clear that they do an important job.
You will see:
In the book, they make clear their views on the matter.
Were I to suggest you avoid this usage in that form, (which I do!) you would probably find many other respondents to your post crying me down.
So, keep watching, and see what other respondents DO have to say about it.
There are other ways of phrasing this: if not of the 'make it clear' variety, then 'clarify', or 'clearly+verb' such as 'clearly state/write/outline'; or ' a clear +noun' such as 'clear statement of'.