How would you rank and remain #1 in a very low competition niche that's likely to grow in competition soon. Competitor is using an expired domain 301 redirect.

I'm in a niche that has really low competition.

I've been able to rank #1 for some keywords by having better content and making useful blog posts, getting a few links along the way.

However, I have a new competitor.

Ahrefs shows that my competitor bought an expired domain and 301 redirected it to their site. The expired domain was somewhat niche relevant and my competitor has gotten to the top of search for one of the keywords and top 5 for a few others, 12k+ dofollow backlinks within 1 month.

I have about 200 naturally in 10 months :D. I'm still on the first page and #1 for all but 1 of the important keywords (although that may not last if I don't plan appropriately).

While annoying, I can't hate the player really.

Curious to hear what you guys would do in a low competition niche to grow and stay ahead of new competition in the future (there will be a lot more eventually)

Some additional info:

I have found and bought 2 expired domains that are in the same niche, primarily to prevent other people from having it. I don't know if I should 301 redirect relevant pages to strengthen the backlink profile on some of my blog posts (12k of competitor's dofollow backlinks are pointing to their homepage, very little left to their blog posts).

The 2 domains have pretty good backlinks for the niche, each site has some topically relevant blog posts with a lot of backlinks from sites with DRs over 40.

The expired domains have not been spam blogs in the past (I went through the steps to check, they were owned by active bloggers in the niche).

Never actively used expired domains before so I'd like to tread lightly if that's the route i go, if you have used them before what are your suggestions ?

Do you even suggest using them at all ?