People and organizations, not just on the left but also over 100 influential organizations on the right [2], take Project 2025 as the desired direction for a future Trump administration. Trump himself has endorsed many of the same positions in this document.
Right or wrong, that's why people have made the association between Trump and Project 2025. This is what conservatives as a group seem to want for a future Trump administration. There doesn't seem to be a competing vision for the party, and certainly nothing laid out in 900 pages of detail.
Why wouldn't people on the left make the association between Trump and this document when so many on the right do?
[0] https://edition.cnn.com/2024/07/11/politics/trump-allies-pro...
[1] https://www.newsweek.com/project-2025-ex-trump-contributors-...
[2] https://live-project2025.pantheonsite.io/about/advisory-boar...