To make a successful thriller there are specific elements that must go in the writting. Raising the suspense on the main character is one of the main elements to a thriller. Throughout the story, at least for a successsful thriller, you want the main caracter to grow and learn from the problem that occurs throughout the movie. There can be multible problems going throughout the movie, but in the end there has to be a way to tie it all together, or make a final conclusion without letting anything out. If something is left out, there can be risks of people finding holes in the movie that should have never been there. Which can lead to the film collapsing, and not becoming good. With these elements, the risk of the movie succeeding increases.

https://hunterswritings.com/2012/10/12/elements-of-the-psychological-thriller-mystery-suspense-andor-crime-fiction-genres/