Why do people target you when you slightly show off?

Because in this environment of mutual harm and intense competition, the vast majority of people's self-esteem is "dependent." They don't rely on self-growth to gain strength; they rely on a sense of superiority generated through comparison to survive.
Your excellence is a blow to their pitiful self-esteem. When they can't compare to you, they will resort to defamation, exclusion, and stabbing you in the back to forcibly erase the gap and find psychological balance.
The most resentful are the incompetent. Don't expect mediocres to tolerate your brilliance; they just want to pull you into the mud to prove that everyone is just a piece of dirt.
To rebuild oneself, start with establishing unconditional self-esteem. The strong support each other, while the weak tear each other apart.