The "prom token in layer 2" problem could arise due to various reasons:

Accessibility: L2 systems may have different access mechanisms or APIs compared to Layer 1, making it challenging to collect metrics directly from them using Prometheus.

Compatibility: The existing Prometheus exporters or integrations might not be compatible with the specific L2 solution, requiring custom development or configuration.

Security: L2 systems often prioritize security and may have restricted access or sandboxed environments, making it difficult for external monitoring tools like Prometheus to collect metrics directly.

Decentralization: Some L2 solutions aim for decentralization, with nodes spread across multiple locations, which could complicate centralized monitoring with Prometheus.