Mix this in with plots that should be attributed to malice rather than stupidity, of course, but not all your NPCs should be super-competent all the time.
You probably have several vampires who are liable to screw up at the table, but you have a cityful of potential screw-ups waiting to happen. Botching that Hunting role isn’t just for PCs.
Life is what happens to you while you’re busy making other plans.
John Lennon, Beautiful Boy (Darling Boy)
This goes all the way back to the first edition Masquerade rulebook - Gary is a city in ruins, partially because of mistakes its Prince made, and one possible reason why the PCs are released there is that their sires Embraced them without the okay of the much more powerful Prince of Chicago. So the PCs might be accidents of the Embrace, and their home domain is likely to fall apart with a strong breeze.
It’s easy to make the NPCs reliably competent, to assume they can hunt and feed and carry out all their business with no real trouble, but it’s not really fair on the PCs if they’re the only ones worrying about killing a victim by accident or being betrayed during a deal. Think about how the other Kindred in town acquire blood and money - it makes them more solid, and then you can let somebody else have a bad night once in a while.
LARPs and open-world computer games have emergent play where most of the vampires are PCs and equally liable to slip up, or the NPC drivers in GTA might miss a red light and crash too, but unless you bring out random plot hooks - which Chicago By Night 1 and the original Storytellers Handbook have - you’ll have to work these out yourself.
So another vampire has made a mess, or a mess has happened due to misfortune or the initiative of an enemy. The PCs can find themselves scapegoats for it, or charged (perhaps with recompense of a boon) with clearing it up, or caught up in the general fallout. A bunch of Hunters rolling into town is still bad news even if it isn’t your fault, and you still have to help hide a bloodless body in your favourite club even if you didn’t drain it. (And you only get to look for clues as to who did after cleaning up...)
And plenty of other Kindred and interested parties will notice the weakness and look for ways to exploit it. If the screwup has a title or a nice patch of hunting ground, that could go up for grabs. Equally, if they have responsibilities, those might be overlooked unhelpfully, making the problem worse...
“Uh, guys? Who was in charge of making sure they didn’t make another vampire movie?”
The Kindred dealing with unrelated problems can also add a lot. For example, they remain wary of disease after the arrival of AIDS... and some remember the Influenza epidemic of 1919... and Masquerade elders would point out that the Black Death lead indirectly to the founding of the Camarilla and Sabbat, while Requiem elders look around for a Morbus to point the finger at...