Give PFE credit for not being a party to a cover-up. I’ll bet JNJ’s lawyers threatened PFE with breach of contract for speaking out of turn, and PFE told them to go fly a kite.
The fact JNJ had said no information would be released on either of the two trials until the full datasets from both trials were presented at a medical conference might be why PFE was the one to make the announcement. JNJ was spared having to explain why they were disclosing the results from one of the trials now.
It's also possible neither of them wanted to do it and PFE lost the coin toss.
There are other possible explanations. Granted JNJ has not been very forthcoming lately, I think we sometimes jump to conclusions based on bias.