For vegans, creatine is among the recommended supplements, because the amount that is produced internally is insufficient for most people, so they need some extra amount in food. (The same is true for a few other substances, e.g. choline, taurine, menaquinone.)
I've heard others say it helps with mood, energy, depression, etc. and if that's the case for some people then great. I don't notice it myself but that's just me. Not everyone has the same body chemistry.
Did you try higher dose. You need to take 0.35g/kg body weight for effects on brain, atleast thats the doses that are usually used in the studies. I believe your body will distribute it to your muscles before any goes to the brain, so you need to take a dose that will saturate your muscles and then have extra left over. I take 25grams whereas the usually reccomend daily dose is 5grams
I did a week trial at 20 or 25g/day once. This was after being on the standard weightlifter's 5g/day for a while so muscles should have been fairly saturated. Didn't notice any effect. 0.35g/kg dose seems like way more than our bodies would have ever had even in a prehistoric hunter's diet. For me that would be 30g/day.
As a vegan you dont get any creatine since you're not eating meat, so your body has to make it itself, which requires a ton of methylation and if you're like me and have bad genes for methylation your body had a hard time with it as it is. So by supplmenting creatine you're reducing some of that burden.
As far as sleep goes, high dose creatine has been studied to have an extermely positive effect on brain function during sleep deprevation, better than stimulants/caffine
I think the prescribed dosing for creatine and sleep deprevation is 0.35g per KG, much higher than the typically recommended dose of 5gs a day for muscle. The positive effects on the brain come at much higher doses. Which is perfectly safe for your kidneys, this is a myth (as long as you dont already have poor kidney function).
I also take some creatine, for this reason.