No one can really pin point the exact reason people reach certain heights
A lot of it can be luck plain and simple
The younger generation are definitely taller for reasons Ive said before, these include more hormone laden food, less stress than older generations, it is for example far easier to pass exams nowadays due to the fact they are undoubtedly easier and access to the internet makes research learning a lot lot easier, in general as well their parents spoil them far more and the vast majority get what they want when they want, this leads to a relaxed mood and a happy existence which in turn keeps growth hormone balanced.
Having excessively low bodyfat can stunt growth potentially as can excessive strenuous exercise, the exercise of don't excessively can put the body under huge strain and what little food or energy they are eating is going towards tepairing exhausted sore bodies instead of growing. Poor sleep is also likely a factor as hgh peaks when you sleep.
Endocrinologists cannot accurately predict a persons height, I remember numerous peiople at school who were told by doctors they'd end up this or that because of certain factors and I can't recall a single case where the doctor was right.
Hgh if taken early enough and in enough amounts during growth years can help people grow taller, the sad reality is because of the cost of it it is usually discouraged, when it is administered it is done so in amounts which typically make little or no difference as it's neither frequent or high enough. I wish to fk I had taken it when younger, I'm certain I'd have been 2.5-4" taller. I was a very very poor sleeper when younger I'm convinced that had something to do with my adult height. I also possibly burnt way way too much energy exercising