Why is the tomb of Sayada Fatima Zahra(a.s.) hidden?
I know she asked Imam Ali(a.s.) to not show her tomb for some guys who have tyrannize and abuse Her and Her family.
What is the goal of not specifying her tomb?
Shiite scholars have suggested many reasons for this:
First of all it was the choice of Lady Fatima(a.s.) to have a clandestine and overnight funeral and that her grave whereabouts be kept from public knowledge. Only her husband Ali Ibn Abi Talib who buried her holy body and her children knew about her grave whereabouts and didn't disclose it to anyone as she had wished.
Another reason was that her enemies and people who usurped Fadak (a property of hers) would not be able to attend her grave later; She had dismissed legitimacy of Caliphs and disregarded them during her life.
That her graveyard wouldn't be exhumed by sworn enemies of Prophet's Holy Household.
As she had intended to awaken and enlighten people about the Caliphs' oppression of Imam Ali(a.s.) and herself, by keeping her grave whereabouts a secret she wanted to express her eternal displeasure at Caliphs who treated her and her family with cruelty. She wanted every Muslim to be prompted to wonder "why is Lady Fatima Zahraa's grave unknown?"
Why Fatima's grave was unmarked, we don't know. Nothing authentic tells us the exact reasoning.
It was old Arab tradition to not mark graves with name and date of death.