I added "Signal", "Matrix", and "Session" to compare competitors. Looks like only Telegram and Signal are benefiting.

https://trends.google.com/trends/explore?date=now%207-d&geo=...

Your link is for Netherlands only.

Worldwide it looks like Telegram is benefitting. https://trends.google.com/trends/explore?date=now%207-d&q=te...

Thanks! I just edited the parent's link and didn't notice.

But isn't telegram less secure than Whatsapp (at least in terms of the lack of e2e for the former)? Or am I missing something?

Yes, going from WhatsApp to Telegram is a sidegrade at best. Probably a downgrade for most people, since Telegram is unencrypted by default.

Telegram has the great advantage that you can have it working on multiple devices at the same time. Whatsapp's web and desktop solutions are terrible.

On the other hand, voice calls on Whatsapp are far better.

I thought Telegram offered e2e encryption.

It's optional and disabled by default for 1-on-1 chats and not available at all for group chats.