Journey Builder, when configured in the entry event accordingly, listens to the run of an automation, not individual activities.
Your automation schema contains multiple automation activities from which you expect a result. This expectation is incorrect. You should get ONE injection into the journey once the automation is finished, which is your step 11.
So what are your options?
Either: question the latency requirement. Run hourly, inject hourly with one automation.
Or: Run four automations in a 15 minute offset. They do not "wait" for each other but run independently.
Caution. automation runs are technically billable, although not currently enforced. This seems to be a safeguard against abuse at this time, which is not guaranteed to stay like this. To give you an idea, one hourly automation consumes around 8.7k runs per year. Corporate Edition offers 45k. So you have around 5 hourly automations in that contractual setup. This pattern would use four for one single process.
Or: Run two alternating automations that call each other via SSJS and execute the sql + fire sequence, and you can even save yourself the wait, theoretically. automation runs are still technically billable, and this could be a LOT of automations, even more than in the previous pattern. Use this VERY sparingly. How to trigger an automation from another automation
Or: Question the pattern of using sql / automations entirely and instead leverage the API & API Events.