I hope that those on Reddit/Twitter/in the media will consider this. It is my analysis of what I've read and what I remember hearing on Saturday. It is not the complete story and there are specifics I am unsure of or do not know. My apologies I am only getting this done now and didn't do it last night (or sooner).
UPDATE: TriMet has complained that audio clips of communications don't tell the whole story and get taken out of context, but has responded by only releasing clips themselves--nothing better. I was expecting complete communications leading up to the service suspension that would give a good picture of what was going on and what operators felt they were supposed to do.
TriMet releases audio of driver, controller communications during rain storm (Portland Tribune)
TriMet releases audio from day of MAX flooding (KGW TV)
FURTHER UPDATE: MAX dispatch radio indicates problems before flooded train from The Oregonian has at least some real audio, and in it there doesn't seem to be any questioning about whether to continue or not. The article text ends with an operator being the one raising the issue and not wanting to go.
ALSO: KGW says it was either the operator's or manger's decision that the trains to go through the high water. This presumes that one of them made the decision on their own, which may not be the case.
In addition, there does not seem to be a clear, written protocol about when to shut down service due to high water; it seems reasonable to have one given that an inundation from heavy rains, broken water/sewer pipes, etc could easily occur.
My view is that I'm not sure it was clearly understood how high the water had become, and that controllers (and, by extension, managers) could/should have proactively discussed water heights. The train order could have easily included details, and Portland Streetcar started suspending service at last 15 minutes before the last MAX train went through the underpass. Instead, there seemed to be an underlying push to continue on, and operators believed they were to do so. Also, it's not healthy trying to assign blame.