Why "The SQL Server service is down" is a candidate for automatic-failover , however database damage is not?

From the URL below we know that "The SQL Server service is down" is a candidate for automatic-failover.

https://docs.microsoft.com/en-us/sql/database-engine/availability-groups/windows/flexible-automatic-failover-policy-availability-group?view=sql-server-2017

And from the URL below , and we that database damage would preventing automatic failover. It explained the reason why automatic failover wouldn't happen:"When the secondary drops a connection (loss of network, database LDF is damaged, …) the state is updated to ‘not synchronized’, preventing automatic failover"

https://blogs.msdn.microsoft.com/psssql/2013/04/22/how-it-works-always-onwhen-is-my-secondary-failover-ready/

So it mean that when disconnection happen between the primary and secondary replica, the state is updated to ‘not synchronized’, and from the secondary URL , we know that "SYNCHRONIZED IS THE ONLY STATE ALLOWING AUTOMATIC FAILOVER !!! ", so state in  ‘not synchronized’ would preventing automatic failover" , I admit it make sense..

My question:

"The SQL Server service is down" wouldn't cause the disconnection happen between the primary and secondary replica? and the state wouldn't be updated to ‘not synchronized’ after the disconnection ?  If both database damage and "The SQL Server service is down" would cause disconnection between primary and secondary  replica ,and cause the state is updated to ‘not synchronized’,  why "The SQL Server service is down" can be the candidate for "automatic failover"  , however database damage wouldn't?

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