Breakdown of shourai watashi wa kagaku no kenkyuusha ni naritai desu.
Questions & Answers about shourai watashi wa kagaku no kenkyuusha ni naritai desu.
Because the verb なる (“to become”) takes its resulting state with に. The pattern is:
• X が Y に なる
Here 私 (implied subject) becomes 研究者 (marked by に). An object marker like を would be ungrammatical, since なる is intransitive.
