The US have the means to act against the ICC. They have a motive for doing so. The US has the Hague Invasion act. The US is currently performing a blockade against ICC. The US really is the main threat.

Why not proton, or fastmail, or tuta. Some provider that resides in a country that does not have an "Hague Invasion Act" just in case the ICC investigates a US citizen.

Maybe not the 'main threat', but most certainly a threat. Have been since 2002.

> If you run your own server, you might not know that you've been compromised.

You may or may not if run your own server. In a case of the hosted solution you are absolutely can't know.