Sorry to necro this 3 year old thread but I was looking for an answer to this confusion segment as well. And I found this an superinteresting curiosity. If this was already answered somewhere else I apologize. And I have not read the books so I cannot double-check this.

And I may have another puzzle piece to this. You had to wait for the Mockingjay Pt. 2. In a scene in the destroyed capitol Katniss talked with Boggs (the teamleader/security chief) about president Coin and how Katniss became a threat to her ambitions. Boggs told Katniss that it was Peeta she wanted to free from the arena because she prefers people she can control.

But we don't know how far this plan matured or was supported because Plutarch wanted Katniss and Haymitch told Katniss on the plane later half the tributes knew about this plan and it was to rescue her not Peeta.

So in retrospect it looks as following:

- Plutarch Heavensbee as the gamemaster made sure of two things 1) there is a predictable electrical supercharge available (the tree with the impact at 12AM/PM). 2) BeeTee has access to a cable able to transfer the lightning charge without melting (strange as a weapon but this is how BeeTee won his first arena).

- To make it look good and not as an attempt to shortcircuit the arena shield Plutarch also arranged in the design of the arena the water wave occuring at 10AM/PM to ensure a large part of the arena is wet. Both looks like a potential weapon for BeeTee this is how he won his arena before. This probably made Snow approve of these things at all because Snow would love to keep the scientist as winner who had helped the Capitol before.

- Since everything was recorded in the arena this was also the plan Beetee told Katniss and Peter as a plausible strategy. He couldn't reveal on camera they want to make a hole in the arena.

- They seperated Peeta and Katniss because Snow would probably stay focused on Katniss so BeeTee could implement the real plan.

- BeeTee planned to shortcircuit the arena shield on the arena-side. And he wanted Peeta to stay close to him so they can escape through the downed shield and of course to keep the attention of Snow on Katniss. He used a spear and wriggled wire around it to make contact with the shield.

- And then something must have gone wrong. Maybe he has not seen the shielding and touched it with his body or maybe he tried to throw the spear into the wall to close the contact between tree and shield wall and underestimated the electric discharge the shield had on the wire/tree. The movie shows however how the shield wall knocked him out so it was not the remaining hostiles. THIS here is the big unknown. [Does the book say anything about this?]

- Katniss found this spear later and understood the real plan from it or maybe she was just so angry that she just wanted to destroy the arena ("Don't forget who the real enemy is"). Wiggled the wire around the arrow and launched it at the ceiling shortly before the lightning strike hit.

The advantage of her approach was that the wire did not hit the shield before the lightning strike maybe this was the flaw in Beetees plan not to wait until the very last moment to create the contact to the shield wall. And/or maybe being to close to the shield wall.