But for a user, iOS Safari (not Safari for MacOS) doesn't show any certificate warning that the user can accept, like other browsers. In fact, it just fails absolutely silently. You'd have to connect it to a Mac and open up the developer tools on the desktop's Safari, to see the errors that are being printed on the JS console.
Otherwise, you'd just be left wondering why it just doesn't work like all the other browsers.
Chrome pops a warning, but (with a few exceptions) doesn't let you just navigate through it (there's a secret key sequence you can type to override it, but it's both purposefully undocumented and periodically rotated to make it something that you can only know if you have the chops to read the source code or consult the relevant developers' forums).
It is true, that in recent versions of iOS (in the past five years or so), you have to install the certificate in Safari, then go to Settings->General->About, scroll all the way down, and manually trust the certificate (to ensure you really know what you're doing by enabling it). And iOS doesn't make this known anywhere outside of that special menu three levels deep, I suppose to not confuse people who had an attacker install a cert on their phone somehow.