They said that 97% of their users are already on subscriptions. I get that local vault users are disappointed, but there's an app for you and it's called Bitwarden.
I think 1Password made a smart business decision. By cutting loose the need to support local vaults, they can focus more development energy on other things that 97% of their users will appreciate. It's a numbers game.
That said...Electron? Ugh. I already spend half my day grumbling about the Slack app.