The parts are just normal parts of a human being that have perfectly normal needs and wants. The drive to get those needs met is strong... for a child its very survival hinges on it. So those child parts are driven by a need that feels as desperate and intense as survival itself.
Because they can't see that the compassionate part of you can help them (because the compassionate part of you has never been able to before because you didn't even know how) they probably believe that if T can't be that parent for them then no-one can. And because the inner drive to fulfil those needs feels like a matter of life and death, it is only natural they would want to fulfil them in whatever capacity they have been able to meet any of them in past, even if those ways might be destructive.
This is where the compassionate adult self can help, once you have learned how. And your T knows how to help you do that.
All is not lost. It is the very opposite, in fact. Your T knows how to help you find your way out of this.
Of course it feels impossible to help those younger parts yourself at the moment. You haven't learned how to do it. Yet.