This may be over-egging AOB's impact a little bit.
It'd take a lot to overcome the issue of the Knights needing to overpay for new signings. That may just be a fact of life at the club. Nathan Brown definitely seemed to have more sway with potential recruits than AOB does I suppose, but it probably helped a lot that we'd cleared the decks cap wise first... and every player brought in under him, the secret sauce in getting that player over the line may have been the one weird trick of offering way more money than everyone else. Connor Watson got $600K on the back of a *pretty good* start to his career at Easts. Mitchell Pearce picked the Knights because we offered way more money than everyone else let's be real (in real terms, he got a higher % of the gap than Brown, by a fair bit). And signing Ponga, well, no one had offered that kind of money to a kid with so little experience before. That deal was a massive punt. I've also heard disturbing chat about the kind of money Brown offered old old Matt Scott & Paul Gallen to come to the club... but got turned down anyway. There just isn't a period in our history where the Knights are a destination club, unless we were ready to really open the chequebook, and even then that has often not been enough. That's just a fact.
I definitely don't think the style of footy we play right now is appealing to new signings, but I suspect the #1 reason AOB hasn't signed that many players, and the mixture of players he has signed is guys nobody else wanted + middle of the road experienced blokes on overs, is probably because he's coach of the Newcastle Knights, and the Knights pay overs for everyone.
This is the way it is for some clubs no matter who the coach is.
Isaiah Papali'i got overs to go to Penrith and that's four premierships in, led by what may now be regarded as the premier coach of the game, and the money they have to spend to keep their core players is higher than what say the Roosters (and Bulldogs) are allegedly paying their guys. Brian To'o makes over $800K I've heard, for example - I think he's worth it, but no other specialist winger in the comp makes near that. They had four players on a million or more, or thereabouts, in addition (Cleary, Yeo, Fish, Edwards). I wouldn't say any one player has really bent them over a barrell price wise, but likewise I'm not sure any players have "done them a favour" the way Roosters players always magically seem to. And this is the best team most of us will have ever seen. About as great a situation as a player could ask for. Yet they've haemorrhaged great players more than any other club I've seen... and make up the difference with their exceptional player development.
Ricky Stuart is this legend of the sport and has never been able to get an elite player in their prime to the club despite trying over and over again. He has good players in depth now but honestly I think the secret to that for them is that they've gotten guys in young, and clearly their recruitment guys have a great eye for talent. But they too aren't getting discounts from their long term players, and their new signings are expensive. Why did Joe Tapine and Hudson Young go there, fundamentally? Because the Raiders offered a lot more money than the Knights could at the time. They overpaid for young talent they really liked, betting on their ability to correctly identify a young player who would go on to be elite. So basically their signing philosophy is almost that they behave like they would if there was a draft - they chase high upside young talent, where it could be years before the signing pays dividends - they just "draft" their young players by poaching them.
Two clubs clearly doing a lot better than the Knights at putting their roster together, and it's in spite of it being very hard for them to sign new players, and usually needing to overpay to bring new signings in. Heaps of players just don't want to live in Penrith and Canberra, and heaps don't want to live in Newy. Newy should be more appealing than either of those towns but seems to be regarded about the same for whatever reason (hearing Dane talk about when he was signed, to him "Newcastle" just meant "mining" and "industry"... he didn't know there were any beaches for example).
I don't think a new coach fixes that and all of a sudden we're picking up Payne Haas and Jahrome Hughes in the coming months. The fix is internal development and savvier talent ID/recruitment of untried young players. Long-term decision making over trying to fix things immediately after every bad season.