Use common sense. Ragnir and Loki clash, and Ragnir decides that Loki is someone he can trust to take revenge on Imu, which Ragnir himself clearly does not believe he can do. If he just wanted a relatively strong ancient giant who could use the Nidhogg fruit, he could have let pretty much Elbaf king eat it. There´s no shot that Oda has Ragnir waiting for someone to reach an arbitrary power level of being kind of close to him, he´s clearly going to wait for someone stronger than himself, or at least equal.
Fixating on Loki´s hammer is clearly directionally incorrect, the point of the scene is that Ragnir is quickly overwhelmed and submits to Loki.
He´s:
>clearly briefly knocked out,
>Literally crying out in pain
>Now believes Loki is the savior he´s been waiting centuries for
The idea that Loki would be weaker than his literal sidekick and pet for even a moment is obviously inherently ridiculous