I wrote more about this in another comment ("Postmortem"), as I developed a similar idea from Mid 2022 to early 2023, but made different decisions.
OpenAI had a serious focus on this that did see adoption; as early as Spring 2021 this was in their docs (linked by others), but more crucially, they quickly added an Answers endpoint(https://platform.openai.com/docs/guides/answers) specifically for this use case (query against uploaded files).
The creator of this project did almost everything perfectly, for sure. They had speed, UI, a converting page, found virality. But they also had timing: OpenAI had banned this open-ended use case till that time, they got lucky that people did not develop Explainpaper competitors, and ChatGPT improved quality while reducing run costs by 10x right when they came into this area, meaning many companies that fore-aware of these changes would have taken it's place, were not trying to enter the market (OpenAI approval was hard, and the costs of models before December 2022 were literally 10x as much for decent quality, making it unprofitable)
OpenAI had a serious focus on this that did see adoption; as early as Spring 2021 this was in their docs (linked by others), but more crucially, they quickly added an Answers endpoint(https://platform.openai.com/docs/guides/answers) specifically for this use case (query against uploaded files).
The creator of this project did almost everything perfectly, for sure. They had speed, UI, a converting page, found virality. But they also had timing: OpenAI had banned this open-ended use case till that time, they got lucky that people did not develop Explainpaper competitors, and ChatGPT improved quality while reducing run costs by 10x right when they came into this area, meaning many companies that fore-aware of these changes would have taken it's place, were not trying to enter the market (OpenAI approval was hard, and the costs of models before December 2022 were literally 10x as much for decent quality, making it unprofitable)