CAs aren't the ones pushing for the shorten cert lifetimes, it's the Browsers. ICYMI, the "tech companies" like Google and Apple are the ones pushing for this and they pretty much control the browsers at this point.
Indeed, and they control the CA/B Forum. The last CA to express an independent and reasonable view got booted from being a trusted CA.
It's like the FIDO(?) Working Group and passkeys. "Don't you try to offer exporting or sharing passkeys between devices or we'll revoke your ability to be a trusted origin for relying parties", meanwhile "Oh, Apple wants to offer this via AirDrop? Step right up." Rules for the big boys, not for you.