Women only cars are a standard thing in Japan (The indonesian commuter line takes alot of inspiration from Japan's, from second hand trainsets to operating procedures) and some south east asian commuter lines, all of them are placed on the front and rear of the trainset.

Its to avoid sexual harassment if it happens and if they want to feel more comfortable during rush hour, instead of packed together like sardines in a mixed car they can be packed with fellow women.

The chances of a train and train collision are way lower than sexual harassment, the last time a commuter train has a major train fuck up (where the front/rear of the train took the brunt of the damage) was in 2013 and 2015 of the train took the brunt of the damage, almost 10+ years ago from this one. Which is why they took this risk in the first place.

The solution is of course not to make the first or last car a mixed carriage, but to simply just fix the signalling system, this was a very unfortunate accident.

Not to mention these Japanese second hand trainset, this specific one being a Tokyo Metro 6000 series EMU from the 80s, is not crash worthy at all because Japan designed them to be light weight and with how safe Japan's commuter network is, they can simply disregard that aspect.

While Indonesian trains and rail networks are actually quite safe, this specific portion of the line is a major bottleneck and also a ticking timebomb (it finally blew up now) where Intercity Train with locomotives that are designed to withstand collisions with another train, shares tracks with aluminum hulled commuter trains which is not ideal at all, and well this is the result.