The phrase "original vision" refers to the original idea or plan that someone has for something. It's like the initial concept or goal that they set out to achieve. Full definition
The trio's original vision for the company was quite different; they wanted to create a fantasy music league in which participants could build their ideal record label. (entrepreneur.com)
With many films the director's original vision fails to make it to the final cut. (sensesofcinema.com)
However, the PS4 was more capable of approaching the lofty original vision we had in mind for the game, so, in the end, I made the decision to switch. (gravityrushcentral.com)