What I'm asking is how tf did text messages and whatever in the walkie talkies ignite a spark strong enough to ignite the PETN?
Pager with firmware that activates an output on date/time X/Y and triggers an ignition signal. That signal is sent o an actual detonator in the device, which sets off the explosive.
Radio with DTMF receiver that activates an output when, for example, touchtone 4 is received over the air, or alternatively if the radio has GPS, another date/time activation via firmware.
Both of these things are relatively trivial for a nation-state to pull off.
So yes, in both cases it's possible that faulty devices are still around. However, if all the rest of your group has had exploding pagers and radios, most people in the same group would have dropped their still-working pager or radio into a bucket of water by now. There's probably a few, and they're probably being carefully taken apart right now to see how it was done.
Afaik such an idea was nonsense previously.
It's not nonsense, it just takes planning and resources. And now that people know it is possible, buying and using any sort of equipment for your group without having the nagging concern there might be a bomb in it is impossible. And that's a pretty powerful limiter.
Hahahahahahahahahahaha
(Pause for breath)
Hahahahahahahahahahaha
Only if you count "most of the online solutions" as "run SFC /SCANNOW and if that doesn't work, just reinstall your OS".