You are absolutely correct emergency fund is very necessary before going into any investment in case there's a challenge but then again, sometimes it's not really necessary to keep emergency fund before doing any investment and if I may ask how much will one keep as an emergency fund? Cause sometimes even the emergency fund don't use to be enough to solve problem(s) since we all know this why waiting to keep... Before venturing into Bitcoin investment and I want to let you know that there are people who didn't keep emergency fund but they are really doing well in their investment so we shouldn't sound like this is a criteria one ought to meet before going into investment though it's good but lack of it shouldn't be a barrier because the truth is we can't actually keep everything ready.
An emergency fund is like a back plan, it shows that one is fully prepared for a worst case scenario, every business person or investor needs an emergency funds that would act as a life support in a case where the business or investment goes wrong due to certain circumstances, for instance a case where someone invest on a pump and dump asset, the person won't go back to square one, cause such person would fall back to the emergency funds and try to fix things up, all the person has to do is get information on the right assets to invest on.
From my own reasoning, I don't see anything wrong in setting aside an emergency fund before making an investment, it's like preparing ahead, taking note of possible unfortunate circumstances and setting aside plans to tackle it when it occurs, and I think the amount required to set aside as an emergency fund shouldn't be generally specified, it could be spare money or money derived from a side hustle.
The amount one set aside might not be enough to solve future problems, but would go alone way atleast solve some part of it, if not half of the problem. Well not everyone see it as compulsory to plan ahead, but then we shouldn't deny some prove that emergency funds have also rescued some people who's investment went wrong and they had backup money to fall back to.