Why didn't the bomb detonate earlier?

During the beginning of the 2014 version of Robocop Alex Murphy is severly injured by a car bomb when he is forced to check his car at home after the car's alarm system activates at night. But this car bomb was actually planted much earlier when he was visiting his injured partner at the hospital during the day. This is even emphasized when the two corrupt cops tell Vallon that Murphy will be at the hospital during the day, providing an easy chance for getting him out of their way.

So why didn't it detonate earlier, seeing that the bomb was to some degree smart enough to detonate when he was near and to drag him to the car in the first place (no matter if due to a smart arming system or a remote-controlling bad guy). I cannot see either an in-universe reason in the story why the bomb didn't detonate (or was detonated) earlier, like at the hospital or on the streets, nor a story-telling based reason why it had to happen at home at night (apart from the fact maybe that if he had been inside the car while driving it could have been more effctive, completely killing Murphy).

So is there any explanation I have overlooked in the story or any other reason why the bomb detonated at home while planted much earlier at the hospital?

plot-explanation robocop-2014

Best Answer

Depending on which version of the conspiracy you accept the choice makes sense.

Omnicorp have two motivations: they don't want pushy cops like Murphy causing trouble; but they need a good cop for the Robocop prototype. The second motivation suggests they don't want to kill Murphy: they need enough of him to be left over to be reused in the Robocop project. There is hint that they identify suitable cops before they are injured (I can't remember the exact part of the dialogue where this is revealed without rewatching the whole movie, but it is there).

This is consistent with how the bomb is triggered. First the car alarm is set off to entice Murphy out of the house. The bomb doesn't trigger until he is near the car making his injuries certain but his survival possible. Presumably this is done remotely though this is not shown. If you accept that Omnicorp is deliberately maiming cops to generate fodder for the program, then this makes sense.