Maybe we could do a survey of old mobile phones and pagers to see how many of them have explosives in them. I never thought of myself as a terrorist but if one of my phones wound up with a small bit of C4 in it, that would be a finding.
Ever wondered how much Israel uses their 8200 alumni it has embedded in all major tech corporations? Maybe this is part of it. Embedding backdoors, and plausibly deniable bugs, or giving access directly, exfiltrating data, whatever.
Why would you need to be elite? That's your own assumption.
There are two conditions for compromise. You're in the position where you have opportunity/access. You are willing to do what's asked.
For the hezbollah attack, it wasnt detectable because they used a very small amount and they used PTEN which is harder to detect than other explosives. Even still there is a lot of speculation online that they might have detonated earlier than planned due to being discovered
That pager thing was a tactical operation with clear goals and a defined time frame.
Spying on other countries on the other hand had always been a thing, the US spying on the German Government is an example that became very well known back when it was discovered here in Germany.