The reason why Discord is popular is that it is much more useful in exchanging information than other sites. Although the telegram was good at first the demand for it has decreased due to the increase in the number of scams. Discord can be downloaded for free on Microsoft Windows, Mac-OS, Linux, iOS and Android and can be used without downloading in most internet browsers. So popular for exchanging text and voice channels and media on a Discord server.
What have scams to do with anything? Youtube is full of scams and people still use it.
In Telegram all you have to do is ignore any messages from random strangers saying "hi", and in the event they send you an unsolicited link/ad/referral you push the block button with the report spam function. When enough people do that the account gets penalized days in read only mode on first offense.
If you are in private group and your privacy settings are done correctly, such thing never happens.
To me Discord takes ages to load while TG desktop is instant. Of course whatsapp is worse, there can't ever be anything worse than that.