yes, i have defeated wysteria but it never said why lord bramble stole it. so i'm wondering, why did he steal the spiral cup? my prediction: he entered the tournament and wanted the spiral cup so bad. unfortunately, he lost in the finale and was so angry, he snuck into the tournament hall and stole the spiral cup for himself.
The reason was to frame you, the Ravenwood participant. Now the real question is why did he want to frame the Ravenwood partipant? Bad blood with Merle? Wanted to reclaim Wysteria back for the plants? Possibly under the direction of someone elses master plan.......
Chester Droor was the culprit who stole the cup he was enchanted by lord bramble to do so.
lord bramble wants Wysteria for him self and if he stole the cup he thought the games would be canceled and everyone would leave and he could take over Wysteria quietly....(whose gonna miss a pound or two of bacon).
well it did work out that way cause that snoopy lil wizard from Ravenwood was gonna win that trophy and find out who took it.
I thought they explained it fairly well. Lord Bramble wanted to frame you, not just to get you to leave, but to cause bad blood between Wizard City and Wysteria. If the two worlds were estranged and/or hostile to one another, Ravenwood would likely not hear about or send support to Pigswick when Lord Bramble made his move to take Wysteria back for the plants.
Yes they explained it very clearly at the end. People just get too clicky with their quests and miss the important details. Bramble wanted Wysteria back so he steals the cup to discredit the school and frames your wizard so that Ravenwood will become hostile towards Pigswick. If the real wizards don't come around anymore, then the plants can take over.