Note that their paper includes p-hacking so this is proto-science rather than science. They didn't find data to match their hypothesis, but they were able to find a hypothesis to match their data.

> Follow-up secondary analyses were then conducted to examine in more granular fashion the timing of the association between nuclear testing and occurrence of transients. Table 2 summarizes the association between occurrence of transients and different time windows relative to nuclear testing, ranging from 2 days before a test until 2 days after a test. The only association that reached statistical significance was for the association in which transients occur 1 day after nuclear testing.