A lot of candidates have the same issue. It can be solved with deliberate practice, i.e. exercises that are tailored and focused on your specific weaknesses.
Without knowing your specific problem, I have two suggestions that should be able to help.
1. As a consultant, I suggest you always start with conclusion/recommendation, you lay out the structure on how you reached that conclusion (i.e., it is supported by X, Y and Z) and then you go through the facts that support each branches of that structure.
How do you practice this in reality? Use the framework I just gave you and use it when reading exhibits. Another option is to do issue trees (you should do both types of practice).
You can read Barbara Minto's Pyramid Principle. It helps in understanding how you should communicate. But if you don't have much time, focus on practice only. Deliberate practice beats “reading about the subject” on any given day.
2. You should practice writing in bullet points. This is what consultants do the whole time. Now, there is something specific to writing in bullet points. You have to write them as short as possible. After that imagine it is still too long (e.g. you don't have enough space in a slide or page) and need to further summarize / cut words.
Now do this with each of your “stories” (and yes, you can use the STAR or SCR frameworks) and “why's” (why consulting? why this company? why you?)
3. In my experience, many candidates are not concise because they don't know when to stop. They convey the idea, and then they explain in several times repeating themselves or giving unrequested and unnecessary detail.
What you have to do is to “hear yourself", understand when you are doing this and STOP. Instead of repeating a second time (or going down to the 3rd or 4th layer) you should ask the interviewer if you were clear and if the interviewer wants you to give more detail on any part of your answer.
Feel free to reach out if you believe you would benefit from a session focused solely on this specific improvement. By the way, this is a skill for life!