Although I empathize your experience towards the recent event but sadly you voluntary agree on this kind of prank by joining his signature campaign because of his written rules quoted below.
I did voluntarily agree on the signature campaign but not the prank.
▶️ I reserve the full right to add/remove any participants, push/cancel/reopen the campaign, or edit any rules of this campaign
Does it says anywhere that you will be pranked by me whenever I want to. What you have quoted is a generic terminology of every BM.
The answer is already lies on the rules.
He has the full right to push/cancel/reopen the campaign, or edit any rules of the campaign.
He reopen the campaign to the new one and change the payment rate with higher rate then reverse back after April fools by doing same method. That’s already satisfied all the action that he did on the prank. You said that you already agree on this rules, Regardless of the prank side. This is really what happened on his recent action.