I did not know that solar spots were linked to flu epidemia, but it is a long time knowledge that solar spot were linked with wheat price in England.
Explanation is simple, it is climate. I imagine flu is also related to cold weather like are high wheat price.
Lack of interest in a subject may be detected by lack of replication or publication, but delay can be explained by failures to replicate.
What I know from Galileo, is that even if he have good ideas, his evidences were quite weak , and he have many problems to explain. His instruments was very hard to use. Finally he was a very ideological activist and was attacked mostly for that.
Attack to LENR can be explained by many facts, from pathetic errors, experimental difficulties, wrong category of experimentator used as references, patent wars, budget fights, theoretical groupthink, incoherent answers to theoretical questions, awful communication, community battles, politicians involvement, journalist prides...