I need an explanation on my hardcore world

ok so basically i had a hardcore minecraft world and i was doing pretty good i had neth ingots diamond armor and was about to kill the enderdragon but while exploring a cave i died to a creeper i had low hearts but didnt expect to get so easily killed and after dying i was lowk so mad i closed minecraft and didnt play minecraft for a few days but then today i decided to make another hardcore world but i seen i forgot to delete the one i died in so i joined just to see the death loading screen and just to go in spectator mode to fly around but i somehow was alive i had everything i had before i died and i even went to my base to see if it wasnt a glitch or something but nah its literally like i got a second life i even see the creeper explosion that killed me im legit so confused about what happened is this even real?? (btw i do have optifine and a few texture packs but thats it)