How To Steal A Subreddit

Hello,

I'd like to know how you guys create new subreddits to take place of other ones.

There is already subreddit that is made for my niche with 70k members,

I started a sub niche subreddit like if the niche was

r/outdoorgear

I made a r/hikingboots

I niched down, but tbh I just want to invest my time in a subreddit that covers the whole niche,

I just wanna replace them.

Any Advice?