'which proved essential' is a grammatically correct and usable phrase in written English.
You can use it when you want to describe a particular element or aspect of a situation that was important to the outcome. For example: "The rigorous training program, which proved essential, helped our team become more successful."
Soon I began writing plays and acting, both of which proved essential in overcoming my painful shyness.
The tau, which he found in the mid-1970s, was the first evidence of a third "generation" of fundamental particles, the existence of which proved essential for completing the so-called standard model of particle physics.
It exploits the complementarity between solid-state Nuclear Magnetic Resonance (ss-NMR) and Powder X-Ray Diffraction (PXRD), which proved essential for performing a complete and accurate solid-state characterization of the two commercial products, and for obtaining new insights into the complex quercetin solid-forms landscape.
In particular, this intermediate space (Maciocco and Tagliagambe 2009; Tagliagambe 2008) also represents the field of action of urban design, which extends its horizons in favour of knowledge neglected in city design but which proves essential for exploring different ways of conceiving of the space of inhabiting.
(One of the technologies affected by the decree was the transistor, which later proved essential to computers).
Tax relief which has proved essential to many small and loss-making research firms is to be extended to larger businesses - but only if Brussels does not regard it as a breach of rules on state aid.
To play duck on a rock most effectively, Naismith soon found that a soft lobbing shot was far more effective than a straight hard throw, a thought which later proved essential for the invention of basketball.
Because of this, New Orleans held a common ideal which ultimately proved essential to its survival a local patriotism that embraced everything from trombone solos to jambalaya platters and held it against the generic and the mundane in a feat of resilience.
Our analysis has been performed by computer algebra tools which proved to be essential.
Secondly, collecting the date of vaccination allowed avoiding misclassification of those vaccinated but not protected, which proved to be essential during the pandemic season.
The enriched GO biological processes and pathways were found mainly related to regulation of cell death, apoptosis, cell proliferation, and metabolic process, which have been proved essential to cancer development.
