Protiviti Manager interview questions

The interview process felt like an endless amount of hoops to jump through. I applied through a recruiting firm and was told I'd have to submit an AP style test (correct the errors in sentences) as a first step, then there'd be a phone call and in person interview. I did each of these things an moved on to what I thought were the final stages. I was told by the recruiting firm that they were preparing an offer. To my surprise, I then had to have four more follow up interviews via phone, each lasting anywhere from 30 mins to an hour. One of which the hiring manager forgot about and had to reschedule. I also submitted additional work and writing samples and emails explaining my current position. After spending so much time interviewing, taking time off work and making myself available, I didn't get an offer. The reason I was told I didn't get an offer was because of a few missed corrections on the AP style test - which could have been addressed much earlier, since this was the first step. The process was extremely frustrating. I would not apply to a position at this company again.