So the person had been reported to the authorities....
...five years ago (and possibly more recently).
It takes quite a bit of resources to keep a constant watch on someone, and even if you suspect something very troubling, if after a while nothing has materialised that is actionable then you have to consider using those resources for investigating something else that has been reported to you. Until a crime is committed there is still the presumption of innocence, otherwise you're simply advocating that we have lifelong monitoring of every person who has ever been reported to the authorities, whether that be a genuine concern or a malicious neighbour, in fact becoming the very Stasi-like state many here are complaining about.
Given that, the authorities have a difficult balance to strike in order to deal with the massive changes in how people communicate that technology has brought about in recent years, how this can then be used by people wishing to generally do harm, and how they can protect us from such people. I'm not saying they've got it correct or are even headed along the right path, and the encryption issue does present a huge dilemma that I have very mixed views on, but they need to try and this is an early step along the way. Regrettably progress will involve making mistakes which will adversely affect people. Hopefully as the technology matures, along with the users and society's attitudes, something will develop that redresses the balance to the satisfaction of all. After all, a century after its introduction we still haven't got legislation or social attitudes that effectively protects people from the risks presented by the motorcar hurling along the highway.