A few thoughts:
1 -- So, these plans, as they are being executed, are not classified. But commercial flights that have already been completed ARE classified? Yeah, that makes sense. [/s]
2 -- One of the guys on the chat was IN RUSSIA at the time. Signal may be end-to-end encrypted, but your personal phone is not. Anything you send/receive/read on your device has been intercepted when on another country's network (which is what is used when in said other country).
3 -- Mike Waltz tried to claim the journalist hacked into the conversation. So, basically, he just admitted that the chat is not secure, even within the U.S.? Kind of confirms item 2 above, no?
4 -- Israel is PISSED that one of their human sources was compromised in this careless manner. Good luck getting that person to cooperate with Israel again!