A little bit of backstory: I quit my job 2 months ago and I am serving my notice period. I had some issues with the management because I did not accept their new exploitative "leadership" and they started to personally attack me. I had a very important role for the future development of the company and quit after addressing these issues multiple times. I am not the only one who thinks like this: Three other (two very important) persons are also in the process of searching new jobs (management and boss does not know about this). To be precise, if the other two people leave, the company is history.
Anyhow, my boss did not take my termination notice very well. He got very angry and wrote an email to me the next day that he does not want to talk to me anymore. However, he demands daily reports from me and always tells me I have to prepare everything for my successor. So I'm writing a lot of documentation and teach my current colleague about my projects.
I asked my boss multiple times if he could introduce me to my successor and he always told me "When it's time". Lately he has written me that he won't introduce me my successor so I could teach him.
Now the real problem.
My successor called me privately. He's a fellow student from my time at the university. He asked me a bunch of stuff about the work-life balance, equipment, my overall experience and why I'm leaving. I told him the job is great. The perks are not to be surpassed, most of the colleagues are like family and the pay is OK. Since I know him well, I knew he would be a perfect fit as a successor and told him that I would recommend him to take the opportunity.
However, he absolutely wanted to know why I am leaving if I am talking this good about the job. So I told him I had some personal issues with the leadership of the new management but quickly explained that I don't think will be an issue for him because it was strictly personal.
Bottom Line / Question: I tried to cover up as much as possible so I can't be blamed for sh!t-talking and scaring of a potential successor. Or have I said too much? Should I tell my management/boss about his private contact with me in advance so I can't be blamed if he declines? I don't want to put him in a bad perspective or anything.
When looking at a similar question (Asked to speak to prospective employees about a company I'm dissatisfied with) I think I did nothing wrong. I focused on the good things and told him I think he is a good fit.