That's again a good reason why it would be nice to get a visual on fuel injection during cranking. It's all good and well sensors and scopes saying all the signals are correct.....but in strange cases like this, it's good to see with your own eyes.

Likewise sparks on all 4 cylinders.

But again, if plugs have been soaked at all...bin them. They could be part of the problem. Throw some new cheap ones in if needed until it will run