Frontend & browser·Layout, CSS and the cascade
you put the vendor stylesheet in a lower layer and your one-class rule now beats its id selectors.
Cascade layers
Also called@layer
Named buckets declared with `@layer` that are compared before specificity, so an entire body of CSS can be placed above or below another regardless of how its selectors are written. It is the intended answer to the third-party override problem that `!important` used to be. The catch is that unlayered styles beat every layer, so partial adoption inverts the result you expected.