If I give you $100 it's belong to you right or wrong? the same thing apply to naruto and kurama, kurama choose to give naruto his chakra so as the other bijuu's naruto never force them or ask for it they chose to give it to him at the end of the day rather you like or not that power belong to naruto same goes for sasuke they both have they own way of gaining power so jus deal with it. Ps if you need to talk about stolen powers the people you need to talk about is madara,kabuto, and orochimaru