Some of it is luck. I moved to fastmail 15 years ago, so I don't have current experience. However there is plenty of indication that large blocks of IPs get blocked by all the major providers - this is a matter of luck though, most blocks of IPs are not blocked and so you might never have a problem while others can't.

Note that a large part of the problem is if you are blocked there is nothing you can do about it. You can't contact anyone at google to get help.