I think you are overly simplifying abusive relationships. If it was as simple as just spotting these red flags from the offset then all women would go on their merry way. This is not how abuse works, and your entire posts has a tone of victim-blaming.
Firstly, abuse absolutely can come out of the blue without warning. Someone can become abusive after many years of not exhibiting abusive behaviour. This is especially common when a woman is pregnant, or is in the peri/post natal period. It is a vulnerable and potentially dangerous time for women, add into that the risk of abuse escalating when actually leaving the relationship.
Also, assuming there are red flags, people don’t ignore these because they are ‘in lust’. We learn what healthy relationships and boundaries are from our own experiences and those around us when we are growing up. Those that have experienced trauma / abuse (including witnessing domestic abuse) particularly if it was repeated or prolonged, and they were never protected, may normalise unhealthy behaviours because it’s all they’ve known. It can be difficult for those who’ve grown up in safe and secure homes, with present and emotionally regulated parents to understand this. But if all you’ve known is love and security, then it is so much easier to notice ‘red flags’ because it is so alien to you. Abuse and trauma creates a fog so it’s hard for victims to trust their own thoughts and feelings. It also massively impacts self esteem and sense of self, leading people to believe they have deserved to be treated poorly. This is what can make people vulnerable to abuse; but it does not in any way blame them, the blame lies entirely with the abuser, always.
Have you heard of the boiling frog analogy? Often domestic abuse is insidious, it happens gradually over time. It can happen to any of us. By the time the abuse has escalated, the psychological abuse / coercive control has done a number on the persons self confidence and they doubt the validity of their own thoughts. This is how abuse works. And it is never as simple as as ‘just leave’.
I think it is absolutely important to encourage women to be confident and autonomous and empowered, to understand healthy relationships and boundaries, to be able to notice red flags and walk away. All of this should be taught in schools. There should be more help for those who experience abuse at any age, in order to heal and to break the pattern of entering into abusive dynamics. Men should not abuse women and girls in the first place, and should be held to account.
TLDR: Red flags are not missed due to lust, abuse is complex, victim blaming is wrong, men need to stop abusing women.