The events are being routed to other event tables like em_event0001, ...em_event0006, rather than storing in em_event. So business rules defined on em_event are not being triggered.
It should not matter if the events are stored in child tables like (em_event0001, ...em_event0006). We use a concept called table rotation for which we split up em_event into multiple child tables and store the events in these tables.
If you would like to trigger business rules on em_event, the business rules need to be defined on em_event, and they should be triggered irrespective of the events actually being inserted on tables like em_event0001, ...em_event0006.
The most probable reason why the BR was not triggered could be due to bulk updates. Some connectors use a mechanism called bulk update to insert the events into em_event which do not trigger any business rules.
In order to disable bulk updates to the em_event table, you can set the MID server parameter "mid.probe.event.queue.use_bulk" to false.