I think being successful makes hiring easier because you can source better candidates, and being big makes hiring easier because candidates are more likely to know people at the firm who can use referrals to work around otherwise broken systems.

It’s perhaps also worth noting that lots of companies used to copy how Microsoft did interviews and later they copied how google did interviews so clearly there were some ideas that those companies were good at hiring. (I’m not sure this strategy was that good. The problem for the Microsoft or google type companies is filtering out acceptable hires from a deluge of applicants with acceptably low errors and costs; the challenge for less desirable firms is sourcing candidates who are both high quality and not about to be hired by Microsoft or Google)

One company that comes to mind when I think about being good at hiring was one that recruited a bunch from my university around when I was graduating. Their particular specialty was hiring illegible graduates with a lot of potential (eg classicists, science students without little programming, etc), training them well, and effectively underpaying them a bit for how skilled they were (which only worked out because the UK has a pretty shit job market for tech and because those people liked working there). I think it was more effective for them than trying to hire the same computer science graduates as everyone else would have been.