In the initial pitch presentation, investors are keen to evaluate the following:
1) Does does concept have a business case
2) Is this a great team that we can bet on
If the answers to the above are positive, then they would be interested in knowing the details of the story, including the marketing strategy.
In the initial pitch document/presentation, the high-level story of what you are going to do, how you are planning to do it and how you will make money is what you should focus on.
Of course, you need to have thought in detail about your marketing strategy to talk about it in case that question is asked. But an initial pitch presentation document is not the place to share a detailed marketing strategy.