Why are gains so easy to lose? After two months where i couldn't

you will be back at your original form in two months

You only lost marginal muscle tissue, the reason your lifts fell so much is your muscle memory is gone. Get back on the horse and your gains will return in weeks.
Unless you were legitimately huge, of couse. Then it's a constant battle to keep muscle from disintegrating

You won't lose much muscle mass if any.

You just got weaker and probably lost weight. Get back on the horse.

For me the only thing that really suffered was bench and that was badly. I started spamming rows though and they're now higher than they were when I was over 30 pounds heavier.

Not too happy about the bench but I also don't work out 6 days a week anymore. Lucky if I get 2 days a week now.