Christianity is the source of the victim mentality. Prior to Christianity, victims were considered to be stupid chumps who deserved what they got. But once you had a victim that claimed to be God, a God who could punish you for all eternity for having victimized him, that started a new narrative about victimhood. With the triumph of Christianity, victimhood became the source of ultimate divine power.
So, now everyone wants to be a victim. Christians want to be martyrs, but they can't find anyone who cares enough about Christianity to want to kill them. So, they make up narratives about Christian persecution because it feeds their ego to be Christ-like. The stories are absurd (see here, here or here), but even the Pope pretends it is true, because the persecution story has historically been so powerful.
Post-Christian populations simply adopt and adapt the narrative, dropping all the God references, but keeping the powerful victimhood mythos rolling.
Unfortunately for the post-Christians, victim mentality is the ultimate self-betrayal.
The character never develops, the story never ends.
You're just stuck in an endless doom loop of personal hell.
That's why the liberal victimhood mentality doesn't work. They have no god to extract them from the doom loop. The only source of power in a godless victim doom loop is victimhood itself: if you lose victimhood, you lose power, so no one can afford to NOT be persecuted. Christians at least retain a god who can ultimately pull them out of the victim doom loop and elevate them above it. Sure, it doesn't happen until after your dead, but there's a source of hope in Christian victimology that is totally lacking in liberal victimology. Christians can break the eternal cycle and reach a personal perfection somewhat akin to Hindu/Buddhist nirvana, while liberals have no way to break out of the cycle without ceding everything they wanted to gain. Liberals have to be permanent victims in a way Christians do not.
Now, neither victim mentality is ultimately sustainable because neither one conforms to the actual reality of the current situation. Persecution requires unjust punishment or at least unjust negative sequelae. Christians really aren't being persecuted to any significant degree, and liberals aren't persecuted at all. Remember, persecution is unjust consequences wreaked on an innocent victim. If the consequences are normal, logical, reasonable and justified, then it isn't persecution.
The LGBTQ crowd get the natural consequences for acting out an addictive lifestyle. Marxists/socialists get the natural consequences for trying to enact an incredibly stupid, childish economic fairy tale. As the poet Stephen Crane might have said, jumping off a cliff and finding out gravity is real isn't persecution, it is simply solid contact with an indifferent universe.
At this point, the social problem is obvious. Victim mentality, whether the liberal or the Christian version, is not ultimately compatible with social cohesion. This is part of the reason Christianity is failing. It's very success has removed it from victim status. Once the victim status is gone, Christians have no way to image the victim God at its center. If Christians aren't victims, the whole rationale for the world view and lifestyle is.... gone. For Christians, God is the source of truth. The truth is, Christians cannot image the crucified Christ if no one is willing to crucify them. No one is.
Liberal victimhood suffers from a very similar problem. If it ever gets out that liberals aren't being victimized, if people realize liberals are actually just stupid people making poor decisions in the physical world, the entire liberal power base collapses.
At this point, the only force upholding the victimhood narrative is national government. Governments now base their power in "protecting the little guy", the victim. Governments cannot afford to let anyone realize that there really isn't much persecution going on. To stay in power, they have to manufacture persecution, so they can still claim a protective function. Thus, for the last few decades, governments have been identifying various "victim" groups, rallying forces to protect them. Once that group becomes powerful enough, government identifies another group to "protect". Setting one group against another is the only way to stay in power, and keep the money rolling in. But that game cannot be played forever.
Truth is the natural enemy of modern victim status. At some point, the victimhood game will collapse, because none of it is true. Jews aren't victims of Muslims, Muslims aren't victims of Jews, liberals aren't victims of conservatives, Christians aren't victims at all. The center cannot hold. Victimology worked for a couple of millennia, when there really were outside forces intent on violently enforcing identity politics, but endless wars have killed off a lot of the most violent genetics in our global society. Victimhood doesn't work in peaceful societies. We need a new organizing principle. It isn't clear what that will be.