It seems so very implausible to me that one of the most experienced and most revered intelligence agencies in the world would fail to recognize security cameras as a viable threat to their operation. Seriously?
What seems more likely to me is that they were sending a very clear message: even with one of the most advanced surveillance and counter-intelligence networks in the world, we can still put two dozens operatives on the ground, run a complex mission with military precision, kill the target, and disappear before you know it's happened. There's nowhere you can hide from us.
Why would they jeopardize the identities of so many of their agents? Would they have bothered with disguises at all if it was intentional to be "caught"?
I don't believe an intelligence agency like that would be dumb enough to be so brazenly open. They didn't want to get caught, but they did.
I think they simply doubted the diligence on the part of the investigators. If you watched the video, you'd know how hard it would have been to put all the pieces together.
The very clear message they've actually sent is "We can expose our agents and make ourselves look bad internationally. Also we can steal the identities of foreign nationals giving us further diplomatic problems.".
What seems more likely to me is that they were sending a very clear message: even with one of the most advanced surveillance and counter-intelligence networks in the world, we can still put two dozens operatives on the ground, run a complex mission with military precision, kill the target, and disappear before you know it's happened. There's nowhere you can hide from us.