I'd say Lisp is S-Expression based, and it's easier to make both text and graphical interface to S-Expressions than to the syntax of typical text based languages.
By Apple's decree and app store policy, any programming language on the iPad that isn't purely based on the JavaScript interpreter in the web browser isn't allowed to download and run executable code, much to the frustration of Alan Kay, who is weary of people comparing the iPad to the Dynabook without acknowledging that Apple left out and prohibited his most important idea on purpose: user programmability.
If Carmack's visual Lisp is implemented as an iOS app with locally running native code, and not purely in JavaScript running in the web browser, then he has to build it himself in XCode on his own Mac for his own use with his own Apple developer certificates, and he isn't allowed to distribute it on the app store.
If you can implement your language purely in JavaScript, like Snap! or the web version of Scratch 3.0, then it'll run everywhere, and isn't an iPad app, just a web app, so it's not bound by the restrictions of Apple's app store. That's the way to go if you can.
https://snap.berkeley.edu/