Complex sentence: However, these were subject to more scrutiny and indeed it was one of these, the Assyrian reliefs, which led to their exposure and arrests, which suggests that the longevity of their scam was concentrated on the passing off of lower level items.
Split into simpler sentences: However, these were subject to more scrutiny and indeed it was one of these, the Assyrian reliefs, which led to their being exposed and caught. This suggests the longevity of their scam was concentrated on the passing off of lower level items.