Missing something
I think what the first judge failed to recognise was that the fuzz had observed him going to Islamic extremist fundraising events in addition to making threats on YouTube so my impression is that they were trying to nip a potential terrorist in the bud.
I find a lot of police prosecutions are ill thought out and often flawed because they go for easy prosecutions for easy wins to keep the numbers up but with this one, the kid seems to have been getting sufficiently hot under the collar to need a figurative bucket of water throwing over him tocool him down.
If somebody makes death threats against you, it is best to take them seriously until you know better or have removed the threat.