The reason they didn't release Chrome for arm64 Linux almost certainly wasn't about technical feasibility, but rather about it being worth the support costs.

The Android arm64 Chrome build is clearly worth it to them, as is the Chrome build for ARM Chromebooks.

Before this point they probably didn't think that arm64 Linux was a worthwhile target to support (especially since Chromium was available on arm64 Linux anyways).

I'm not sure what has changed in the desktop/laptop ARM Linux market that changed their minds - or maybe they want to put their shoulder behind that market.