First and foremost, while we should kind of take into account the safety of the participants, the safety of the audience was more important. And yeah, there were a ton of ways to bring tension without involving explosive putty since one fatal mistake with armed C4 could wipe out both the participants and the audience—where some participants weren't even supposed to die.
In addition, the goal of these events now had shifted to cater for more entertainment value compared to standing in between that and Darwin's Theory.
Because while seeing a random dude blow up could still be considered fun, with the world's population, it'll only be a matter of time before we run out of dudes to detonate—unless we resort to blowing up children for sport.
We just have to find the sweet spot for excitement and near death and we'll be good.