Just FYI, Signals are actually derived from Observables in KnockoutJS. React was originally created as a response to the first wave of JavaScript Frameworks which heavily relied on two-way binding-- remember the whole emphasis on "unidirectional flow"?

Signals recently became more popular as people observed the performance and DX that they made possible in SolidJS. Solid's creator, Ryan Carniato, has acted as a bit of an evangelist for them-- even working closely with the Angular team.