Researchers will (and have) find effective ways to share research results w/o traditional publishers. This would surface very quickly once access was temporarily revoked.
Or Elsevier’s belief that the opposition is tenuously formed. If temporary free access prompts a critical mass to decamp, Elsevier will have staved off both permanence and precedent.
I don't see how granting free access unilaterally improves their negotiation position other than goodwill in manipulating the executive and legislative government..
People tend to become politically involved (loosely defined) when desperate. Remove the source of desperation and engagement fades. Convincing people to come to a meeting or go to a rally or draft a letter to the dean or call or write to their representative gets harder when the problem goes from specific, e.g. I need X study to write my paper, to abstract.
(Well, technically, there was a short one at the start of last year IIRC, but Elsevier prolonged access then just as well.)
Some fraction of the people whose support is necessary for the negotiators to remain empowered are. The question is how many.