Well if you actually have gone on dates etc simply vanishing is rude. But if it was all online, I don’t consider it dating, I don’t think people are obligated to respond. I did online dating when I was younger and I got so many messages that I couldn’t even read them all. Let alone respond. Not like I am that great but when you live in a busy area that’s what happens. And if You exchanged few messages and felt uneasy why would you explain anything, they could be aggressive for all you know. If you are already dating in person then of course it’s rude, unless again you feel unsafe.

Yes if they are long time friends it’s different but is it possible they don’t look at online friendship this way?

I am not trying to tell you not to be upset but there might be no need to be upset. If they don’t want to talk, then they don’t. There are always people who do

On the other hand during pandemics id worry if people don’t respond. I’d think something happened