Don’t assume so. Events like this are not isolated, and when women start fighting back, it often results in a moment of hesitation in the attackers, pausing to ponder if their potential victims might be armed.
They usual assumption is that they would just take this into consideration when continuing the attack; but often this is not the case, because the majority of such attackers are cowardly, and if there is even a possibility that they could be harmed, they instead look elsewhere.
Rapists especially, are believed to be trying to use rape to *dominate* their victim. If their intended victim fights back, it makes domination incredibly hard.
Since many more states in the US have become gun friendly, especially with concealed carry, there has been a strong decline in violent crimes. However, some violent criminals have indeed changes their tactics to initiating attacks with a sneak attack to disable or even kill their victim. But this is done out of fear, and it is only a small fraction of the violent criminals out there. When they are taken up, it pretty well ends it.
The bottom line is that right now, girls and women are being violently attacked, raped and even murdered, without struggle. Any resistance they could mount at all would strongly raise the “degree of difficulty” for their attackers, beyond a point many are not willing to go.
It adds a burden to being a violent criminal which should not be considered a bad thing.
All of what you suggest is great in theory, but putting it into practice is another matter. What is going on now in Scandinavia is something fairly recent and it can be attributed almost entirely to Muslim immigrants.
The bottom line is that right now, girls and women are being violently attacked, raped and even murdered, without struggle.
Where in the article does it say that the victims were not putting up any resistance?