The underlying premise is that "these dumb sand people are too stupid to have carefully planned and executed a complex mission, the truth is that wE kNeW aBoUt It in advance but no one listened. Here take a look at these 'secret reports' by unnamed intelligence officials."
It reminds me of the ancient alien shit of how "there's no way the stupid ancient egyptian skull brains could have made the pyramids, it must have been advanced aliens who showed them!"
Or another thing I hear is "Israel has the most advanced spying network, hOw cOuLd ThEy NoT hAvE kNoWn???" Ok well the resistance fighters completely owning all their "high tech" shit (or how Hezbollah sent a drone over big cities and completely avoided the Iron Dome) proves that maybe their systems were actually shit and not really "advanced" in the first place.
Another thing ppl might say is "well why would Israeli media leak or talk about it? wouldn't that make them look bad? thus maybe it's true?" Think about it, what looks worse: completely getting owned or saying "oh yeah we knew about it but someone forgot to mention it up the chain." They're obviously lying to make themselves look better. I hate that some commentators I see know that Israeli media lies but then when it comes to these "bombshell" reports they completely believe them. It's sad, because it plays into the racist trope that the Palestinians are actually stupid and any military victories are "actually we knew about it but stumbled somewhere"
Suppose they did know beforehand, had the plans, but didn't take any measures to mitigate the risk.
You don't think that makes them appear incompetent or malicious? If they knew in advance but did nothing, that would be admitting to permitting the deaths of their own civilians. That's not exactly good PR, like you suggest.
One thing that states hate to lose is the monopoly on violence. The best way to prevent (overwhelming) violence that will imminently arise in bourgeois states is to scare the larger class into submission or win it over with concessions. Narratives like "knowing" about Oct. 7 can be used to scare people who would otherwise join resistance groups away from doing so. Not so easy to see in this case, but it's more clear when looking at how certain people cast the CIA and the NSA as all-powerful and all-knowing. Even the detractors of the alphabet agencies sometimes end up reinforcing this narrative. It's true that they do possess a wide variety of resources, but they are still made up of humans and will never be perfect. My point is that yes it could be used to make someone look malicious or incompetent (by their detractors), but it can also reinforce the "invincibility" or a "precognition" narrative that will be later used to dissuade resistance (by supporters or by detractors).
I think what OP wants to say is that maybe they never suspected a thing or maybe it was brought up as a point in some morning standup meeting in the IOF that the "filthy hamases are plotting something" and everyone ignored it. One thing is clear: the attack was not planned by Israel, and they did not have perfect knowledge of it - and those that repeat that last line are clearly coping.