Chromecast not working on iPad, but works fine on iPhone

what i say is that ios devices support airplay in the os

with things like chromecast it's up to the app to support it, so google home or chrome for ios or the likes

why google would alter the behavior of their app between their iphone and ipad version I can't say, if it was me then I would try using chrome or other google apps which would support chromecast to narrow it down as to if it's google home for ipad which has some limitations

and maybe check googles support pages Meet the Google Home app - iPhone & iPad - Chromecast Help

ios devices does not native support chromecast the app has to support it native or one needs to download some of the chromecast apps in app store