First sentence of TFA.

This is not a claim that all trilobites were made extinct by volcanic ash, but that these fossils were the result of an ashfall, by which previously unavailable anatomical detail was preserved. The headline is misleading, but even the shallowest read of the article would have mooted your speculation.

But the new info about the mouth parts is extraordinary and could still lead to big discoveries and earthquakes in taxonomy. The problem with this animals is that all the mouth pieces that fossilized were from different types or in different positions compared with all arthropods alive or extinct that were not trilobites.