Hi Kedreeva!! You mentioned that male peafowl get aggressive when hand-raised, why is that?
There is no research done on this to be able to definitively give an answer. I've written about this before, as well, but I'm feeling chatty.
However, according to anecdotal evidence by keepers around the world, after being hand raised male peafowl treat humans the same way as they would treat a rival peacock they hold a grudge against, and the aggression is almost always worse during mating season (exception cases where it's bad all year). This would seem to indicate that instead of seeing themselves as humans, peacocks see humans as "like them" ie: peacocks, and that the aggression is hormone based.
With peafowl, a male will attempt to chase off unrelated rival males. Related males form leks, but even males that have not ever met before seem to be able to clock blood relations (this actually was confirmed in scientific study, which I have talked about before so you can find it in the peafowl tag somewhere), and whatever method they use to do this, it cannot apply to humans (because you're definitely not able to be blood related to them). As such, the solution is only EVER going to be: chase off. But, humans are not going to be chased off by a bird they are keeping in a pen, and so begins a feedback loop of stress and aggression: they try to chase you off, they can't, they get frustrated and stressed and more desperate, rinse and repeat. This eventually, even with no reinforcement from you, leads them to be stressed even just seeing you, whether or not you're interacting.
However, most people I've seen aren't just "not doing anything," they are actively reinforcing the idea that they are a threat to the bird. They yell, they make sudden movements, they kick them, they pin them to the ground, they chase them around/carry them around, they spray them with hoses, they attack them with sticks/rakes/pool noodles... I have seen the gamut. And ALL of it reinforces the idea, to the peacock, that they are DANGEROUS and should be CHASED OFF. The bird physically cannot escape in many of these situations (being penned in a flight pen), so the only option they would see is fighting.
This is ALL solved by just... not hand raising them. When they don't consider you to be a rival cock, then 99.9999% of them will be chill dudes even during mating season. They don't actually LIKE to fight, but there are certain situations which inform their instincts (instincts strengthened greatly by hormones) that they need to in order to survive/reproduce.
There is ONE potential work around I have found for hand-raised males, if it is not already too late, and that is extensive training. Stan was, by necessity, hand-raised due his medical issues early on. I trained him to jump to a treat perch when he was young, and once he got aggressive, I was able to reinforce the treat perch such that when I went into his pen, he would immediately go to that perch and he would get treats when I left if he stayed there. This didn't eliminate his stress over my presence, but it did alleviate altercations between us, and allow me to care for him properly. I have helped two other people do this with their young hand-raised males (ones they didn't know better about, and won't repeat), so I know that it CAN work for some others, but it's never going to be a good solution compared to just not fucking doing the hand raising in the first place. The birds will still be experiencing stress they shouldn't have to, and the owner will experience stress knowing that aggression is sitting just beneath the surface at all times.