Sure, but if I understand it the story wasn't that the didn't avoid it, they went out of their way to get to the tower. That's different.
We don't know the whole story, but to me it sounds worse.
The players are told that they see a tower in the distance, and only know that the tower is dangerous. Keep in mind "dangerous" is adventurer speak for interesting and profitable.
Presumably, they don't have any pressing business or more interesting hooks, so decide to check it out, as adventures do - when presented with something interesting.
We're told that the group didn't do their due diligence in scouting the place, but that's a second hand account. We don't know what they actually did/didn't do or what the DM signposted, if anything.
We do know that they tried to sneak in, met with something and the ones that didn't immediately flee, immediately died.
That to me seems a waste of an interesting adventuring opportunity. Especially if it was a new group where the PLAYERS didn't realize they were in over their heads.
Now, again, maybe the DM flat looked at the group and said: this place seems evil and truly, truly deadly you feel dread just stepping into the grounds something EPICALLY bad dwells here - just so you know. And the group moved on anyway - in which case, well ok. But somehow I doubt it.
And even still, this is the perfect opportunity for the DM, thrown a bit of a curve ball, as opposed to the one usually throwing them, to have a different type of scenario entirely. One where the big bad throws the group for a big loop and recruits/blackmails or otherwise conscripts them Or something to that effect. Wiping them out is just a bit too obvious and short sighed for the litch.