I'm copy pasting a reply I did on another thread with a similar idea, so you can try to adjust around the following:
Some cant be changed, some can like underwear positioning.
Post:
I'm very curious on this topic, throughout years I've been doing research and while I don't think there's a clear explanation, the following may be causes:
(Though please note I have no medical education, this is just what I've noticed throughout a lot of medical-oriented videos, discussions and experiences from people)
1. Masturbation grip - Depending on how you grab your penis while jerking off, over time you can produce micro trauma that makes it curve a bit to one side or so.
2. Underwear positioning - Depending on how you position your penis in your underwear, as you grow up and boners happen while you sleep your penis gets used to being in a certain position.
3. Peyronie's Disease - A traumatic event that made the penis develop scarring tissue and therefore causing a bend.
4. Suspensory ligament - The penis is held by a ligament called suspensory ligament, this one can also affect the way your penis curves while erect because of the pressure it causes on it. Some penis lengthening surgeries actually cut this ligament so your penis can be more freely outwards but this can lower the incline of your penile curvature.
5. Genetics - Certain racial genetics can make a difference between a longer and shorter suspensory ligament which can make the penis curve change.
6. Penis size - The longer the penis the more weight meaning its more possible it gets used to a downwards curve.
7. Weight - Your weight can affect your testosterone, meaning the healthier, fitter you are the better erections you can get.
8. Type of underwear - If you were more accustomed to loose boxers, its more probable your penis while erect had more freedom to raise while more constricted clothing could create a downwards curve specially if pushed towards certain positions over a long time.
9. Masturbation location - If you are more used to masturbating in the toilet you would probably aim downwards into the toilet to ejaculate, meaning after many years this could cause a downwards curve; while if you are more used to masturbating while in bed, you would probably aim upwards to ejaculate on your abdomen, meaning after many years this could cause an upwards curve.
10. Circumcision - If you are circumcised, your penis skin could've been cut longer in the back than the front meaning your grip would naturally pull harder downwards or viceversa.