I think you need more how-to video content vs theoretical explanation. How to source motors, how to source batteries, what batteries are best, what is a converter, etc. I think if you ramp up the video production, maybe find a local shop or other local youtube content creators working on cars to collaborate on a project car. Essentially you need to prove to the audience that you can help them on an EV conversion project.

To make it scale, do what other content creators do and create a private, paid content area with more detailed videos or create a paid course people can go through that steps them through a conversion process.