There was virtually zero fabrication. This was something that happened slowly over time and wasn't obvious until the 2024 debate. There was definitely a cover-up but the media wasn't part of a big grand conspiracy. It was by the people close to him, such as his cabinet members. Since when have cabinet members not tried to hide shortcomings of President. People typically want to keep their jobs, so it goes much wider than presidential cabinets.
Also, plenty of media reported on Biden's apparent cognitive shortcomings. It was extremely widespread and we all knew about it and almost all of us admitted it, including liberals.
It's still my position (more than ever) that it's better to have a presidency run by a relatively competent cabinet than a single evil tyrant.