Why can attempts to justify a standard of truth lead to an infinite regress?

In the context of skepticism, attempts to justify a standard of truth often lead to an infinite regress because of the circular nature of epistemological validation.1

When an investigator seeks to establish a criterion for truth, they must determine if that criterion itself is correct. This requires the use of further criteria, which in turn demand their own justification, creating an endless chain of reasoning. If one attempts to avoid this by appealing to "first principles," skeptics challenge the basis of those principles: if they are proven, the proof itself requires validation; if they are claimed to be self-evident, one must still question whether that claim is accurate and whether the principles are being applied correctly.1

Ultimately, this process forces a choice between an infinite regress, an arbitrary stopping point, or circular reasoning—such as the Cartesian circle, where a criterion is validated by a premise that itself relies on that same criterion. Skeptics use this dilemma to highlight the difficulty of attaining knowledge that is absolutely certain and beyond doubt.12