It is called “secondary considerations”.
This is from an important SCOTUS case from the 1960s was called John Deer V Graham. It was about an innovation reading plows.
In the decision was a quote from an earlier case about a pesticide sprayer
“the . . . [device] meets the exacting standard required for a
combination of old elements to rise to the level of patentable
invention by fulfilling the long-felt need with an economical,
efficient, utilitarian apparatus which achieved novel results and
immediate commercial success.”
This resulted in the short hand that commercial success, long felt but unsolved needs, and failure of others were indicia of non-obviousness. Widespread copying by others came in later -
"Wm. Wrigley Jr. Co. v. Cadbury Adams USA LLC, 683 F.3d 1356, 1364
(Fed. Cir. 2012) (“a nexus between the copying and the novel aspects
of the claimed invention must exist for evidence of copying to be
given significant weight in an obviousness analysis”).
The basic idea is that commercial success, based on the claimed invention, indicated the invention was a breakthrough.
From a comment I learned there is an analogous policy in Europe. https://www.epo.org/law-practice/legal-texts/html/guidelines/e/g_vii_10_3.htm
"Where the invention solves a technical problem which workers in the art have been attempting to solve for a long time, or otherwise fulfils a long-felt need, this may be regarded as an indication of inventive step.”