system
Given the following post, respond as if you're commenting on Reddit:
human
[X Men Days of Future Past] How did the Sentinels take over the entire North American Continent without being stopped?

I know Sentinels are good at what they do but there are too many way OPed mutants and heroes to allow this I feel. On top of this the Celestials want to foster the mutant population so the sentinels are a threat and would conceivably be wiped out. My final point would be that Dr. Doom would never allow anybody other than himself to kill the Fantastic Four, But give me your reasoning.
gpt
I will try to tackle this point by point.

1. Sentinels have bee shown to be incredibly efficient and adaptive. Master Mold constructs sentinels of varying sizes some of which can reassemble after being destroyed. Some are built for the sole purpose of hunting a particular mutant, such as nonmetallic ones to hunt Magneto. All of this, coupled with the death of Charles Xavier early on in the DoFP meant that there wasn't a well organized response mounted by mutants and the adaptive and powerful sentinels were able to take over. All other heroes would similarly be unable to tackle such a massive threat without the aid of the X-Men and their expertise in fighting Sentinels for so many years.

2. Celestials don't do jack. If they cared, they would be intervening all the time and they don't. They set up their little experiments, mess with out genetic code and step back and watch us run like rats through a maze. Assuming they are multiversal, the demise of one experiment in one universe would not likely warrant their intervention.

3. Doom would not be able to prevent the FF from being killed. He is incredibly powerful, but again, the Sentinels would overwhelm him. Perhaps he escaped to a pocket dimension and was planning a return, but he isn't omnipotent. Unless the FF killed Doom in this reality before the events of DoFP took place. Remember that in just about every universe we have seen in the multiverse, aside from Earth-616, Reed Richards ends up being evil/crazy. Maybe he was already on his downward spiral and killed Doom, and then fell victim to the Sentinels.