What I see is this (something I also recently saw as a plot element in a spy show).
If you have a choice between eliminating a highly placed individual in a foreign government (or even in our own) and controlling them, which would you choose?
You eliminate them, fine, justice is served, and then, another nasty b@st@rd takes their place. The meanest beetle rises to the top of the dung heap. You have no leverage, no control over the new beetle, just someone else to sort and contend with and try to predict what nasty stuff they will pull next.
OR...
You inform them of what you have, and how easy and unfortunate it would be to destroy them if it were to leak. BUT you can guarantee that won't happen if they do you a favor down the line...
Immediately, they are pulled in, forced to constrain themselves, aware they are being watched. It doesn't stop them from being nasty, perhaps, but may have them doing preemptive damage control and constraining their urges and minding their manners a wee bit.
When you ask, they either comply or are slaughtered in the courts and public opinion, forced to resign or placed up on charges.
In the cold blooded world of spookdom, every op has its collateral damage. but ultimately, control over outcomes is the goal. (We only pray our spooks have our best interests in mind and would not have to resort to such methods, but there is a solid chance that high level people have covered the simple tracks, laundered the money, whatever, and might only have a few urgent and personal transgressions that can be manipulated by (or just not dismissed by) the press so as to be lethal and undeniable intel.
So, eliminate the bad dog, or put it on your chain?
If there are prosecutions, it will be the ones who won't play 'nice', just to act as a warning to the others.