Now we actually know why Rimuru is so much more powerful compared to others. It's likely that he was about to be transferred, but he died so only his soul came over. This led to much more excess energy than the transmigrations of others.
@doomrider7 i could have sworn that in the WN (haven't read LN as i can't find it translated) that
He becomes a demon lord after the holy empire sends hinata and a bunch of soldiers to kill rimuru and everyone else and due to anger/sorrow of losing his friends he kills the 15k+ holy knights (the knights might have been farmas kingdom knights and not knights from the holy empire but because its been so long since i read the WN even more so the ealier chapters of it)which allows him to become a demon lord and that doesn't happen untill after this arc where he later meets ramaris while getting skills for the kids from the fairies so they can keep living and at the pace the manga is going while saying 100 was a over exaggeration its deffinatly going to be 12+ chapter