I'll raise your spark for complete destruction.
Here's an incomplete list that I keep around of the mechanisms that I've observed so far that have played a big part in the decline/destruction of an engineering team (and product thereof):
1. Too-technical leaders:
As startup scales, there can sometimes be a mad dash to fill new leadership roles (e.g. VP of Eng, Arch, CTO, etc.). Super-star engineers present at startup phase sometimes move into these when they are not the leadership type, causing engineering team to devolve into a visionless, directionless zoo.
2. Non-technical leaders:
Inverse to the above - as startup scales, in desperation, new leadership roles are filled with non-technical individuals who have little to no engineering experience. This causes similar outcome to #1 (albiet slightly different, but equally perilous).
3. Problem engineers:
Small number of leaders lack a spine, conducting shallow interviews and let in "problem engineers" who spoil the party and wreak havoc. Lax hiring practices almost always are reflected into non-existent firing practices, leading to them lingering around.
From experience, it only takes around ~5-10% of a team being this type for it to have a large negative impact, as they tend to derail progress, dodge responsibility, reputation farm, push rubbish, all that nonsense. It harms morale, and the skies turn grey in the office...
4. Micromanagement:
Speaks for itself. Leads to red tape, demoralization, timeline slippage and frustration.
EDIT: I'de love to hear how these foot-guns have been avoided. From experience it seems really challenging, as if like magic; as if cultivating and maintaining a good engineering team and culture therein is like balancing a pencil on it's nib...