The Haddonfield murders actually took place in the world of Season of the Witch. The two films that were produced ended up being very loosely based on actual events, thanks to the publicized reports from Myers' old psychiatrist and the traumatized sole survivor - much like Texas Chainsaw's Leatherface is based on Ed Gein.
- Furthermore, 'Michael Myers' or his equivalent in Season of the Witch's world was actually part of a test run for Silver Shamrock's larger plan, using a single mask on an individual to see whether or not trigger signals could be sent to the 'brand marking'.
...was 'only' in the thousands. Some kids stayed out later for more candy; some had families with busted TV's; some were being punished with no TV, and so forth. Needless to say, it was still counted as a horrific event of staggering proportions, yet it was not as bad as it could have been. That said, Cochran was either a pawn of or working for the cult Doctor Loomis faced later in the series. For the sacrifice of the children was enough to resurrect Michael, and make the killer who was previously pain-ignorant and very durable into a true nightmare immortal.
- The death toll would have to include adults. Remember that when we see the 'test run' of the Silver Shamrock masks, it somehow ends up killing the parents of the kid wearing the mask, too; Presumably the death toll could be much higher because events would be made more chaotic by parents being killed as a byproduct.
- Possibly the biggest reason why the death toll wouldn't be particularly high is homemade Halloween costumes still outnumber store-bought ones, and did so to a much greater degree in the decade when this film is set. Most potential targets wouldn't even own one of the booby-trapped masks.
- Let's not forget, a lot of kids probably survived simply because their parents were so sick and tired of hearing that wretched London Bridge jingle that they found some convenient excuse to leave the damn set switched off.
As horrifying as the deaths of thousands, if not millions may be, if the sacrifice had not been completed, a much worse catastrophe would have befallen humanity from the wrath of offended deities.