Not sure what made the diagrams, but I think you've correctly identified the Excalidraw handwriting font. There's two versions, Virgil[1] and Excalifont[2], both under the MIT license.

I think the monospaced font is Comic Mono.[3]

[1] https://plus.excalidraw.com/virgil

[2] https://plus.excalidraw.com/excalifont

[3] https://dtinth.github.io/comic-mono-font/

We've used purely excalidraw. Nice to hear you like them!