Apple switched to zsh to avoid the licensing obligations of GPLv3 required by current versions of bash.

And that is all.

chsh -s /bin/bash

However: Apple still distributes a version (of bash) licensed under GPLv2. You can update it.

No lawyer makes programming decisions for me.

Proof of pudding: Show me a script that begins with
#! /bin/zsh

🦗🦗🦗🦗🦗🦗

Real programmers write scripts in perl. IMNSHO
It does so much more and is 1337.

Csh is from BSD (older than Linux) and is buggier than bash, especially when writing scripts. For more info check out the end of the wiki page on it: csh reception

But I think the bottom line was just that fewer and fewer people are sitting at shell prompts and scripting (and sh) won the shell wars.

That said, I always set my interactive shell to csh and run background stuff with:

nohup program_name < /dev/null >& output.log &

I.e. just add nohup and deal with stdin, stdout, stderr. Not that much to teach your fingers.

If csh/tcsh is not included in Manjaro, I'm pretty sure you could download the source and build it: see https://github.com/tcsh-org/tcsh

Anything which adds something to teach your fingers should be multiplied by the millions, or possibly billions, of people who will have to do "just a little bit more" thousands of times every year to appreciate its real impact.