Never been an issue until then (I must have gone over a year without logging in at some point before then and still was able to log in), and then suddenly 'screw you, a chunk of your past is gone with no way to recover it'.
I was so upset when I realized what happened. I'm still annoyed by it. I know I should have exported it all away a long time ago so it's on me, but I didn't think to do so, I had gotten so used to it always being there.
A year of inactivity before total deletion is way too short for email, imo.
Ask Yahoo. I'm guessing no, since it says "we also deleted all of your emails".
Now it’s time to pay for a good email service, like Tuta, Proton or Fastmail.