Not enough info.
24player or 72player version?
If it was 24player version and you could visually see all 16 players standing around waiting for the nodes without fighting before the nodes popped, then they were definitely using some kind of a cheat or exploit to have full LB. Even if they were fighting each other from the onset... the first nodes only spawn a minute into the match. I find it hard to imagine an entire team having their LBs ready a minute into the match.
Furthermore, you also say that "most" of them had "fever" already. Do you know the difference between the Battle HIGH and Battle FEVER symbols? Battle High requires 4 kills w/o being KO'd and Battle Fever requires 8 kills w/o being killed. If it was a 72player match, then it could be possible for a few ppl (maybe even several) to get Battle High status in one minute (OR a couple Battle Fevers, but not both). If it was a 24player match then it would be incredibly difficult, almost impossible for one to get "most" of their members Battle High Status in less than a minute. I will say it's absolutely impossible for MOST of them to have Battle Fever status in less than a minute. (FYI, I'm basing that on 24players scenario, 8 players per team, I'd consider "most" to be 5/8 or 6/8 members having the status.)
Even if your team was waiting up top, and one team was "farming" the other team down below. I cannot imagine a scenario where "most" of one team could get Battle High status and still have enough time to get up top to the nodes in less than a minute. Especially once factoring in Respawn times, Invincibility times, and travel time.
However, if one team was overpowering both of the other teams in a 24player scenario, then there would be enough player kills to allow for at least 4 of them to get the Battle High status... but that still doesn't explain LBs being ready to go at the first set of nodes. It also wouldn't explain Fever status. At most 2 ppl could possibly get Battle Fever status before the first of nodes if one team wiped both of the other teams at mid. If "most" of them rode up to the first node with Fever in a 24player match... then that would definitely indicate some sort of cheating.
Sounds super fishy to me at any rate. Would need to see a video or screenshots (don't post them here with names as that is considered shaming on the official forums) to believe it.