Sync data shouldn't be affected by Firefox crashing; I suspect something else was going on.

Are your Passwords still present on the other device/s that you have connected to that Firefox Account / Sync Account?

If you haven't checked the other device/s yet, disconnect the device/s from the internet before launching Firefox so that Firefox is unable to connect to the Sync server. IOW, pull the LAN /CAT5 cable from the router / modem.

My history is also gone somehow. No I have not used any other devices connected to Sync yet. You say pull teh internet cable from the router and plug it back in?

So how do I get the PWs back?

Hi

Thank you for your question about the Firefox Sync service.

It appears from your question, that you are using Firefox Sync as a back up service. This is not what Sync is designed to do. The Firefox Sync service takes a copy of the data you wish to include and transfers it to a second device (typically a mobile device such as a tablet or a telephone) running a copy of Firefox. The storage in between all attached devices is both temporary and fragile and is not stable enough to be (and is not designed as) a reliable backup service.

If you have a copy of your Firefox profile for desktop Firefox, you may be able to recover your bookmarks and other data. Please have a read of this article.

If you have a copy of your data on a mobile version of Firefox, please follow these instructions to connect it to Firefox Sync to copy your data.

Yes that's true I treated it like a backup service because I switch devices often and reinstall OSes from time to time, too. Never occured to me that it's not meant to be used like that.