Why Eobard Thawne sent Nora Allen back in time ?

[Spoiler] Cicada had a dagger that could temporarily take away powers from metahumans. In the future, Thawne would get caught because of that blade and will receive a death sentence. The only way to prevent this from happening was to send Nora back to the past so she could help Barry Allen defeat Cicada and destroy the dagger. If there is no dagger which could take away his power, then he would never get caught.