Hi Michael,
I think you should keep your old channel rather than give up on it completely. Since you already have 65,000 subscribers and helpful videos, there is still value in keeping it active.
I would suggest reviewing your YouTube Analytics, focusing on audience retention, click-through rate (CTR), and which videos still attract viewers.
You could also experiment with a few videos while keeping your new channel focused on its specific niche.
Sometimes a fresh content strategy and improved thumbnails, titles, and SEO can make a difference.
Wishing you success with both channels!