I wonder why they didn’t eliminate that dude, long ago?
Possibilities:
1. Better the devil you know...
2. His second in command might be more competent/more evil/better at the job/better connected/etc.
3. Might have been harbored by someone, might have really good tradecraft or even just good luck.
The above are standard reasons - no idea if they actually apply here as I am just speculating.
“I wonder why they didn’t eliminate that dude, long ago?”
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I guess, they were waiting when minimal collateral damage condition arise.