Lady Fatima (AS) was gifted the property of Fadak from her father the Prophet Muhammad (SAWA) by order from Allah (SWT) to make her financially independent to help the believers who are in need. All the wealth and properties of Ahlul Bayt (AS) used to be spent to help the believers in need.
The tyrants who illegally confiscated Fadak from Fatima (AS) did not want her to be able to do that. They wanted to make her look financially weak and unable to help.
The crime of confiscating Fadak from Lady Fatima (AS) has got many dangerous sides including denying her statements and the statements of Ameerul Mo'mineen Ali (AS) and Hasan (AS) and Husain (AS) and fabricating a false narration on the Prophet (SAWA) which was never said by him.