Hold on, what did it predict exactly? Did it say "there'll be a mass shooting in New Zealand, on a specific day" or just "something violent will happen somewhere, maybe"?
You're being taken in by a very old technique; make many, many, very vague predictions. Look at the daily news every day, either personally, or farm it out to your fanbase. Cross-reference the daily news with your library of predictions, and take anything that could possibly be read as predictive. Rinse, repeat. Nostradamus was a well-known offender (or, rather, he made the predictions, his fanbase did the rest). See https://en.wikipedia.org/wiki/Postdiction#Skepticism
This sounds an awful lot like the "When he's right, he should be lauded, but when he's wrong it's because of $valid_reason." Am I summarizing what you're saying accurately?
And if so, I have to ask- is there anything which would convince you that QAnon is untrustworthy and/or full of BS? If so, what would that be?