[Darth Badguy]

If the requirements are not met, you have to met them (duh :P)
For example, to bribe some planets, you need to have done multiple intimidation missions, for racketeering sometimes kidnappig etc... that's for preventing you from just lazy corrupting everything without doing any efforts. To freely corrupt all planets you should at least have done 2 piracy, 2 intimidation and 2 kidnapping missions, which are all tactical. After that, you can lazy sit back and corrupt with pressing on the bribery/corrupt militia/racketering button.