I have to agree with my brother, there are employees I've hated due to certain things but slowly grown to appreciate for various other reason. Like, I had one employee at my previous management job who was absolutely atrocious at customer interaction and various other things. I disliked him at first for always being in the backroom. I slowly grew to like him and be on his side in every argument versus other employees for the simple fact that without him the back room wouldn't have been able to run because he literally did all the inventory/stock management every day by himself. I found out the reason he was getting complaints from all the other employees was not because he was 'horrible and always in the backroom' but that he was always in the backroom because everyone else literally refused to move or arrange stock because it was 'beneath them' and 'Todd Work'. The employee was named Todd and he was quite happy to just quietly do work in the back, I finally had to just tell everyone else they couldn't fucking have it both ways, he was in the back doing stock all day or they did some fucking stock management. They shut up and let him be after a while. Like James said, sometimes your best workers are not the ones first readily apparent who make the most noise and seem the most 'eager' day one. In fact, in my 6+ years of management experience I've found those are usually the fucking worst. Our last batch of hires had a girl who, due to my seniority and ability at my current job and the fact that I get along with or am related to(James) the managers instantly tried to befriend and engage me over video games and various other things and tried to constantly tell people she wanted to do good and whatnot. Basically she was the most vocal/engaging employee. She ended up almost getting fired within 6 weeks, for not showing up or being late over half a dozen times and constantly being incorrect on her till, finally 'quitting in rage due to our 'LACK OF INTELLIGENCE'(What she screamed while walking out the door) after she got written up for no-call no-showing 2 days in a row and then arguing with the manager and using rude language about what she thought constituted being 'sick and unable to call'. After she left all our employee theft problems stopped, all our back room issues stopped...
What I mean is, maybe your boss finally got over everyone who was being vocal/'helpful' and started to see the real side of things. I'm jaded enough by management that I ignored the one girl being 'nice' to me and just looked at the merits of her work and, when asked within the 3 weeks of her starting recommended her for being fired and the 'quiet yet capable' people for being kept on because I realized the 'friendly' girl was really just trying to use fake attitude to cover up horrible work ethic. You gotta be capable and efficient, if you can manage that you'll rarely get fired.