So just how was the whole time loop possible to begin with? Hector 1 doesn't come across the time machine until after he has seen the woman in the woods and was stabbed. And in order for that to have happened, he would have had to use the time machine to set the situation up to begin with.
This. The only logical answer to the question is unfortunately the least satisfying one: it all happened because the young guy turned the machine on.
Riddle for the Ages: Was it really physically impossible to change the past or did Hector actively prevent himself from doing that by following the advice from the scientist? Though the two options are not necessarily mutually exclusive as the advice itself could be caused by physical immutability of the past in the first place (adhering to Novikov's self-consistency principle).