Could you please tell me what's wrong with this question?

Overleaf: PDF causing compilation timeout

• Probably it was downvoted because they thought it was simply a time-out. However, for that reason, they should have closed it, not downvoted it. Anyway, it is well formulated. May 24 at 5:21
• @Emile btw, the timeout problem was fixed in pdfpages, see ctan.org/ctan-ann/id/… (but this won't be available anytime soon on overleaf) May 24 at 8:23

The downvote could be caused by the problems with the provided code. The comment from Ulrich Diez summarizes these issues. Basically, the code you provided will result in errors unrelated to the problem asked about in the question, and therefore anyone interested in answering the question needs to clean up the code first to get to the actual issue. This is what David Carlisle did in his answer. The code sample provided there is the minimal document that is needed to reproduce the error. You should have provided something like that.

The general strategy is to:

1. Make a copy of your original document and continue with this copy.
2. If needed, delete any privacy-sensitive or classified information. Make sure the error you get is still there after removing this information.
3. Then remove all other content from the document that you think is not relevant. Check if the problem is still there. If the problem has disappeared then you removed too muich. Put back the last thing that you removed and remove something else instead. Keep checking if the problem persists.
4. Remove all \usepackage, \newcommand, \def etc. statements that are not relevant. Keep checking if the problem persists.
5. Post the code you end up with after you can't find anything else to remove.

For your specific question this would of course be rather impractical, given that the problem was a timeout - so you would have to do a lot of waiting every time you would check if the problem persists. However, since you already knew it was probably caused by pdfpages you could zoom in to that part of the code fairly quickly.

That being said, the downvote is a bit unusual. Your posts wasn't bad at all except for the problem with the code, and here on TeX.SE a downvote is quite rare, even for posts that are much worse than yours. Also you have been constructive in the comments which normally dissuades people from casting downvotes. Maybe people were indeed thinking that the problem was caused by a part of the code that you didn't show, which was indeed a possibility although it turned out that it is an actual bug in pdfpages. If your code would have been more minimal then this could be easily verified or falsified, but with the code provided it was not so easy to check that it was in fact 'not your fault'. So your question was just a victim of an unfortunate set of circumstances I guess.