It's important this is done openly
... but I can see the argument for letting evidence lead to suspects rather than always insisting investigating suspects leading to evidence. After all, where do you get your suspects from? It's a police state if you always start with the suspects and not the criminal activity.
There's an important and fundamental difference between blanket surveillance of all comms in the hope of finding criminality and the targetting of a specific platform seemingly, openly intended for criminal use; it seems to be of the same kind as an investigation or hacking of say, child abuse sharing servers on the darkweb, leading to identifying the users and operators who would not have otherwise been under suspicion.
Also worth noting that the individuals charged will still be able to make representations about the admissibility of the evidence adduced in their specific cases. I think they have the balance right here.