Why did my collegue/manager suddenly act like this? Is it my fault he left?

For the past 3 years I felt I generally had a good working relationship with my collegue/senior and he often said do too. People said that he spoke very highly of me.

He then became the manager about a year ago and asked me to apply for a job at another base (where I’d previously worked with him). I helped him out by covering a few shifts through covid which he was grateful for. He still covered 3 days over there. He said he would like me to apply as he wanted someone hardworking etc. So I applied. I did moan a bit I guess and said the office was very noisy. Still he kept texting me asking me to apply.

Anyway I didn’t get the job, he gave it to this guy who applied. The guy didn’t want the job in the end, he then asked me if I wanted it but oddly tried to put me off saying that it wouldn’t be ‘rosy’ and that he’s be expecting me to be doing double what I’m doing now

I asked him for the real reason I didn’t get the job he said the other guy seemed more efficient and that he wanted more output from me. He said it was a toss up between someone kind hearted (ie me) or efficiency. So that site employed agency which cost them more.

Anyway for months later he was ok with me I felt he was giving me lots of volunteers to support at one point whereas the others weren’t having them so I put my foot down a bit with this. One day said to me ‘your all the same here, your all care free. You are the opposite of me rachel, care free’. I didn’t say much but he sighed and said ‘it’s a good thing I suppose, it’s good for the social aspect and a laugh’.

About a week later he told me that he was leaving. I offered to help him cover shifts at the other site if that’s what was stressing him and he said he didn’t want me to and that the problem wasn’t just over there it was ‘here and everywhere’, he seemed angry and pointed to my office. A week later he expressed his negative views about the other place and called them all ******s.

Anyway he went off sick for some weeks and has now left. He texted a few times asking how I was and he wanted some stuff I was selling, well he got it for free lol. Then he encouraged me to go for a job I’ve been applying for.

I KNOW this is only work but I guess works all I’ve done over the pandemic so it occupies a big part of my brain. Ive been worrying for weeks and felt ashamed that this is somehow my fault or at least partly. I guess I have been a bit laid back and too comfortable but I also feel I did whatever he asked. It’s been getting me down/making me lose confidence that maybe I’ve been this annoying employee that’s made him change his mindset about me.

I know it’s only work but I feel confused last year I felt that he really valued the way that I worked he always said how good I was etc I just don’t get it. I know it shouldn’t matter but it does to me.

From what you said, it doesnt seem like your the reason he left. I think you may feel paranoid as you stated that work is a big part of your brain. My advice dont overthink, wish him the best and move on. If you was the reason he left, he wouldn't be messaging you, trust me..
From what you said earliar you seemed like an ideal employee whom always goes the extra mile, maybe you might be the reason he stuck around for that bit longer.
Personal advice ( Dont mix personal feelings with work) its the one place where the term " nothing personal, just business " is applicable.

If you was the reason he left, he wouldn't be messaging you, trust me..