So we can't prove it was due to email content. For all we know it could just be a dude named Richard who throws darts at a board full of usernames all day.
I've been using gmail for my domain (free gsuite legacy) for 10+ years though I'm careful to not do anything that could be misinterpreted on the service particularly through google photos or youtube
I actually used fastmail for 10 years prior to gmail but abandoned it in 2010 or so because imap/calendaring/etc. wouldn't meaningfully sync with my iphone but gmail had full free activesync (which I still miss a bit...)
I still keep a basic inexpensive legacy fastmail account just for some sieve scripts and cleaner smtp than gmail offers...
If Google increased their limits to 100TB it wouldn't really make them more attractive to my small business because I can already live within 100Gb without with virtually no administrative burden.
2TB of mail storage represents an extra security risk for us and the chance to accumulate more un-controlled data.
It's much better to get that out of the email server and into something secure and time managed so that it can be deleted when not needed.
You're suggesting 2TB is harder to manage with real enterprise management features and MDM functionality vs a provider who allows users to download a full copy of business emails to their personal devices? I like FastMail features, but if un-controllable data was the real concern then Google Workspace would be my go-to not FastMail.
What I'm saying is that we have a policy to not use email as long term storage because it's considered bad practice. As such we don't gain much from Google offering more storage space because we wouldn't use it anyway.
We're a only a small business and I know that's different once you grow beyond a team you can fit in one room.