Disclaimer: Boring Video.
I made this video just because there is no more chromecast app. Instead, you can setup your chromecast using the google home app.
It's not that difficult to setup the chromecast on a different network if you decide not to factory reset the chromecast:
1) install google home app on your ipad if you haven't
2) Go to google home and then select the top right of your device. You can go into Settings.
3) The click on the wifi option.. and select "Forget this Network"
4) Then proceed with add device at the bottom of google home app.
5) You'll need to go into settings and select the chromecast in wifi.
6) finally go back to google home app and follow instructions in setting up your chromecast