#absolutely normal behaviour

But as the MC became more involved in the Devildom's problems, they started to adopt the same toxic traits that had created wedges between the brothers in the first place. From relying heavily on their pacts to subdue the brothers, to allowing a curse to control Barbatos (even though they had the ability to break it), to going along with the brothers' manipulative scheme to trick Satan into reconciling with Lucifer when Satan ran away to the human world -- it's almost like MC has unconsciously picked up on some of their loved ones' behaviour. Gone are the days where MC brings in a new perspective to problems. Now, they just embrace the chaos and their more darker traits, for that is what is expected of them to survive in the Devildom. And since everyone within their circle puts them on a pedestal, this further affirms to the MC that this is how they should be.

Dealing with the affairs of the Devildom had also caused the MC to grow more apathetic. In the beginning, they had been actively taking steps to form pacts with the brothers and were generally very invested in freeing Belphie from the attic. They remained true to themselves and insisted that they form a pact with Satan based on mutual trust and understanding, and not just as a means to smite Lucifer. Despite being in a helpless situation, MC never refused to give up their agency. But the longer MC gets involved with these shenanigans, the more they grew... numb to everything.

Solomon bringing me back to the Devildom unannounced? Oh, sure. Diavolo and Solomon hiding the reasons for my sudden return? Not my problem.

Simeon facing a problem to the point of having a quarter of the cast acting as his bodyguards? Eh, I'll just ignore it until I can't anymore.

Watching and waiting. That's what they have resorted to doing.

And that mindset of kicking problems down the line until it lands on MC's doorstep and they have no choice but to act -- that's exactly how they have been acting when they were stuck in NB, hasn't it? MC didn't bother forming pacts with the past version of the brothers until they were given an ultimatum, and even then, they simply relied on the convenient timing of each brother struggling with an inner crisis to swoop in, resolve the situation and tick them off their checklist.

MC in NB seems like an unfortunate culmination of everything they faced so far. They're too apathetic to care about getting sent to an unfamiliar place once again, too desensitised to life in the Devildom to reclaim their agency, and too desperate to earn the love of their former family to even think about anything else. They became so co-dependent to the demon brothers that they seem to think they cannot live without them or their affection, even if the ones they are living with in the past are different people from the ones they grew to love in the present.

The phrase "You either die a hero, or live long enough to see yourself become the villain" fits way too perfectly for the Obey Me MC. After all, MC keeps getting rewarded every time they try to get themselves killed (or even when they actually got killed). Maybe that's the only way they know how to resolve problems.