A thesis means another word for writing immensely and unlimitedly. You have to go on and on. When you begin to write, some of the content comes out by itself. As a writer you have a lot of ideas bottled up and initially you find lot of content emerging out by itself and your word count popping up.
But it is not smooth and easy to maintain the flow of ideas and increase in word count after you have written a major chunk of the content. It becomes harder and harder to write as you come closer to the finishing line. Any idea why you think it happens and how you can overcome it?
I think it primarily happens because of all the content that you want to put in your thesis, there would be some content you are good with and thorough and some things which are difficult or you are unsure with. Those things need a lot more thought and need a lot more understanding before you can clear out your thoughts and write something.
Usually when we start writing, we begin with the easy stuff and eventually and inevitably, in the end you would be left with more difficult things to do. It is similar to pull out the low hanging fruits first from a tree and then the higher fruits appear difficult to pull out.
Another challenge with academic writers is the unique requirement of academic writing which calls for supporting details required for every idea that the writer represents. Almost every idea that you write requires some kind of reference attached as reference as part of your research. Having to write the reference creates extra work and hence the writer feels to procrastinate the reference writing job to the end. So, finally what happens is that during the process of completion of each chapter, the easy things get done first and the difficult get left for later. If this continues to happen in each chapter, you end up building a great amount of unfinished work and it becomes one hell of a task to be able to finish the entire thesis. The moment you get the signal that it is becoming difficult to write any further as you are done with the easy part of the job , realise that it is the time to focus on the more fine details and look into the more challenging aspects that you have been overlooking all this while.