And I wonder, is that because all the women on here who have stayed and fought have done so because their survivor is in fact their 'true love', otherwise they would not be on here in the first place?

Yes and No. First of all, I don't believe in 'the one'/'true love'/'soulmate'/etc.
My partner is the best possible counterpart I found, and he's by no means the perfect and neither am I. We're two ordinary people who seem to be compatible in such way that we love each other's positive sides enough to put up with each other's annoying idiosyncracies.
What I don't need in my relationship is a 'purpose' - thank you very much but I'm no mother Theresa and do not have a caregiver-syndrome.
What made me stay is that I think it's unlikely I'll find a better counterpart who has less flaws. My partner still has enough good sides and good character traits that make me want to stay.

In the past I've had relationships that wouldn't have lasted through a disaster like this, indeed they fell apart about much more mundane things.