why does it looks like the prologue and all that happens after that are 2 different games?
In lore, the reason is most likely that
the mc is affected by his mother power which she use to make her perfect little world and the mc must break throuth it to continue on his rampage. (I don't remember how much is head cannon and how much is the actual story.)
If you mean on a meta level and complaints from the community attach to it, I have 3 theories.
-First is that the lore explanation was plan from the start, but the author was to slow to execute his idea and failed to communicate it in the VN and to the community.
-Second would be that the VN was deraild by someone wanting a beta harem protagoniste. I don't know how experience Whitebear was when he started this VN, but an inexperience writer can lack the confiance to go trought with their vision when chalange with someone else vision. In particuliarity, if there is a power dynamic (like a patreon) or if the other feel more confident (like how I'm tryng to look like: it's not like I am a specialist on anything).
-Third might be that a lot of time has passed IRL and the auther could have wanted to try something else and highjack his own story to do it.
While I personnaly prefer the first theory, many that complain seam to prefer the 3rd.