i dont think causality has ever really been a thing in the wider nasu/verse
each and every timeline plays by its own rules despite often diverging from very similar points in history. even as far back as tsukihime i remember the rules behind healing magic changing from one route to the next, and fate/extra is set both in the future of an alt timeline that still had the original games events happen despite wildly different rules in place. to say nothing of the chaos that is FGO, which actively interacts with those other timelines (the seraph event being a sequel event to extra/ccc, which takes place 200 years later in a different timeline despite your own servants making reference to the events throughout fgo; and fate/strange fake has their ishtar steal important plot item from fgo ishtar during the 7th singularity for use in that series instead)
what im trying to say is
all those questions you have about this?
lock em away, throw away the key and just sit back and enjoy the ride. if you're lucky they'll explain them away with the nasuverse's incredibly specific and yet paradoxically vague ruleset