A Casper response is scored relative to other responses to the same scenario, meaning your score is the strength of your response relative to other responses to the same scenario. Placing in the first quartile means that other applicants had a stronger performance. It does not mean you failed, it just means that compared to other applicants, your responses were not as strong. The Casper test pool is full of high-caliber applicants.
Applicants who placed in higher quartiles may have done so for a number of reasons, based on the competencies Casper is designed to measure. These might include:
Effort: they may have tried harder to respond to questions (for instance, they may have explained their position fully, or used the full amount of time before moving on to the next question, compared to applicants who place in the first quartile)
Empathy: they considered all perspectives in a meaningful way
Equity: they show the same high degree of respect for the experiences and needs of others
Communication: they demonstrated above-average ability to effectively articulate their ideas
Familiarity with the medium: they familiarized themselves with the format of the test (video, typed response, etc.) and were able to successfully navigate these aspects of the test.
Whichever quartile your Casper score is placed, it should not dissuade you from applying to any program. Many programs consider all quartiles and use Casper as an additional piece of information among many metrics to make admissions decisions.