I've to retract this question!
I've undergone the same process already in 2019 when the question originated.
I've missed to find my own history of activity here, and can only beg for pardon (a severe illness last year still forces me to review my older activities).
Sorry for this absurd inconvenience.
I first thought to delete this question at all, but it has already answers and the system warned me against deleting question having answers, so I just put out this msg.
The question/answer I refer to is here: https://math.stackexchange.com/a/3125786/1714 It answered the related question as it has been asked in its first version; but some users (including myself) noticed, that the asker very likely might have something else in mind and finally someone even reformulated the question.
A short conversation in the comments around my answer showed moreover arising anger, and even a downvote - so I self-deleted my answer, however a bit frustrated because of the lot of effort I had invested... This all is of 2019, so nearly 4 years old.
Casually I browse the tag and reread (the historical) questions; but when I step into this question I always think that my detailed answer has much value --- but leave things as they are.
Today I think different, and feel a bit "empowered" (? :-) ) by one comment, so I undeleted that answer today.
But looking here in META for some opinion I see now, that a similar problem has been discussed here earlier in 2016 Should I delete my answer after OP changed his/her question in an essential way?
The final advice (as I understand it) was to leave the (later) misaligned answer under discussion ... just deleted.
But I've now another idea: is it perhaps a better idea to "ask the question with its original direction and then self-answer my question"? Such a procedure has been proposed in MSE for certain situations, so maybe this would be the most appropriate thing here now.
What do you think?
I'll leave that answer of mine for the time being as "undeleted" so also discussants with low reputation can see the problem and state their opinions here. I think I'll re-delete it after discussion here in any case.