Maybe it’s my English. What probability do you assign to “seems likely”? Above 50% (the way I read it)? Or does it mean it’s a possible outcome among many others, all with very low probability?

I would read it the same way, but personally I would want to attach an additional qualifier: It's likely that this is one of the causes.

There may or may not be something inherently problematic about the way the MCAS works, but more thorough training would likely have lowered the chance of these accidents happening - having the same type rating was one of the root causes for the lacking training