Yet somehow the power backing their union has historically not been "greatly diminished," at least not compared to other unions.
* A movie/show being delayed mostly has extreme financial consequences for the studio employer, not for the individual writer employees. By contrast, a scientific publication being delayed mostly has extreme career consequences for the individual scientist employees, not for their employer institution.
* The NIH's funding comes from the US government. A studio's revenue comes from the audience. NIH funding is unlikely to decrease as the result of a researcher strike, whereas a studio's revenue will unequivocally decrease as the result of a writer strike.
* Few people outside of the scientific community will directly perceive the consequences of NIH research being postponed for a few months. On the other hand, many people who enjoy watching movies/TV will directly feel the impact of favorite shows being postponed or cancelled.
* As demonstrated in [0], the effects of the strike are already glaringly evident after just a month, and will be even more evident after a few more months.
[0] https://en.wikipedia.org/wiki/List_of_productions_impacted_b...
As you say, even "if basic bioscience research stopped [in its entirety], it would be years before the effects trickled out publicly." If the consequences of a strike are not grave to the employer (even if you could get everyone on board), then the power backing the union is greatly diminished.