Rationality was hip at the end of the 19th century when the intelligentsia believed religious dogmatism was the root of all evil. Rationalism was the logical counter-draft.

The early 20th century proved that humans can also commit atrocities and form dogmata without religion.

Later thoughts relativized rationality, which was a necessary step in my opinion.

We rarely see rationality today even if many try to claim it for themselves.