sorry to hear this - I literally don't let my e-bike out of my sight and have never parked it up in town for this reason.. (I always take my unpowered bike as its only a couple of miles to town anyway)
My local Councillor (a keen cyclist and very supportive of better facilities) had his (unpowered) bike kicked in on the town stands, as I've used the same stands and had no problems I suspect it was politically motivated as he is the sort of man who is very strong in his opinions, distinctive in appearance and might be more likely to make enemies than me, but it is of course still completely unacceptable...
Have you told the cops? (some forces let you report it online).
Even though a bobby may not turn up (if at all) if you get the crime number it makes it easier to claim off insurance and means something has gone down on computer increasing the crime figures in that area, and if enough other people do so an area gets a bad rep and the authorities are forced to take action... the surveillance state isn't going to go away so may as well use it to your advantage...
were there any other bikes nearby? it does worry me though as it seems to hint that its worse than brain dead, as if the vandals had some knowledge of just what to sabotage to really anger an e-bikes owner

(unless they thought the wires were some kind of alarm that could be disabled...)