My theory is that he intended to get the bomb into the stadium and then leave. He had no intention of killing himself. Why else would he still have bomb-making materials in his apartment? What was he saving those materials for? Why didn't he use everything he had if this was going to be his first, and last, bombing?
If he was going to blow himself up, he could very easily have had the bomb on his person. But he didn't. It was in the backpack. So I must surmise he was going to leave the backpack in the stadium and then take off. This plan is what foiled him, as he couldn't get into the stadium because they wanted to search the pack. Had he intended to kill himself and had had the bomb on his person, he would have gotten in. What irony.
Having tried several times to get into the stadium without success, he realized the only way to get the bomb inside was to have it on his person. Even then, he probably didn't intend to die in the explosion, but still planned to leave the bomb and get away. So he decided to go to a quiet spot where he could take the bomb out of the pack and hide it under his clothing without being seen by gate security. He chose the bench, and he sat down to make the transfer. While making the transfer, he accidentally set off the bomb.
If he hadn't accidentally set it off, he would have returned to the stadium, probably to a different entrance that he hadn't tried before, and gotten in. And the resulting events would be all over the MSM, instead of this media blackout we have now.
As usual sir, you are absolutely 100% correcto!
Reportedly, the explosive he used is very sensitive to being bumped or dropped
Alternately, he was thinking of putting it on one of the buses that were parked near him, and messed up when trying to reset the timer
Was he going to set off the bomb by remote control? Maybe his handlers saw his return to the bench and lit him off because they thought he had cold feet.
Your scenario seems highly plausible. The only thing that bothers me is his apparent ignorance of the fact that checking or even prohibiting backpacks has for several years been SOP at many major stadiums, and for longer than that at rock concerts. If Hinrichs was part of a sophisticate doperation, and had trained terrorists as handlers, it seems they might have had another MO.