The issue with the 737 MAX became evident within months of the plane's launch. By contrast, the Dreamliner has accumulated over a decade of flying history across over 1000 aircraft with precisely zero fatal accidents.
The fact that the pilots denied that they had shut the switch (one asking the other why they had done so and the other denying it), and that they restarted the engines should be taken into account. Ok, murder suicide is definitely on the table but I would want to see some other reasons for believing that this is so.
Sorry to nitpick, but for a good Bayesian, absence if evidence is evidence of absence. If you want the aphorism to be technically correct, you should say "absence of proof is not proof of absence".
A note on the terminology: "evidence" is a piece of data that suggests a conclusion, while not being conclusive by itself. Whereas "proof" is a piece of data that is conclusive by itself.
For a long time my wife refused to accept that Tree Kangaroos existed and insisted that I'd made them up. When the internet came along she looked them up and treated me strangely for a while.
What things that you have never seen do you not believe in?
(not the OP) Giant isopods. They're not real. I know there are pictures of what are supposed to be giant isopods but they are not real animals, instead they're clearly fake models of made-up animals.
I do not trust these air worthiness directives 100.0%. The 737 Max also required two catastrophic failures before it was grounded.