Petro's wife just had a baby yesterday. I am sure his primary focus right now is not on hockey.
I have said for a while if he leaves STL it was known he was going to leave prior to the Faulk trade. All the talk throughout the season didnt seem to make any sense. The Blues never put in any effort in trying to resign him. It was widely reported Armstrong didnt even speak with Petro's agent until the team played in Toronoto which I believe wasnt until January.
Everyone knows the Blues most important person to sign after the cup win was Petro but they made several other moves like Faulk and Schenn without saying a word to Petro's agent. That does not make sense under any circumstance unless there is other information that has not been made public.
It could also be something like a contract was already agreed to but they were waiting until after the season to sign it because other moves needed to be made first to stay under the off season cap, but then Covid happened and its thrown a wrench into the plans.
Either way the Blues' actions do not seem like there was any urgency in signing Petro so I think they either knew he what he was going to resign for, at least pre Covid, or knew he wasnt going to be resigned