"...my feeling is that De Menezes was indeed the target."
Depends what you mean by "target". I don't think they knew who he was from Adam.
It was a display of how deliberately ruthless, lethal and at the same time utterly incompetent the system they had put in place was (and indeed still is) and I speak from experience, having been surrounded myself by a team of armed police marksmen with a helicopter thudding above my head and been entirely innocent of any wrongdoing whatsoever. On their past form: Harry Stanley, Menezes... I seriously thought at that moment that my number could be up.
"Cressida Dick has enjoyed quite a ride since then; call me old fashioned, but being in charge of genuine #### ups that end in the death of an innocent doesn't usually result in being promoted to the top job in your field in the country; that treatment is usually reserved for people that get the job done how it's supposed to be."
Dick rose because she had been earmarked and had been previously groomed for high places before the Menezes debacle: lots of "accelerated promotion" for the accountancy manager with impeccable Oxbridge connections; female... lesbian: she ticked all the necessary elite middle class plus many of the 'diversity' boxes on a political level; The mess she made wasn't going to be allowed to override that.