This is the best answer, IMHO. Also, network effects means that everyone's already on WhatsApp, so it's only natural that people use it more than Telegram
Do you mean the whatsapp chat SERVICE being back doored or the software? Because we can audit the software super simply in Linux to see what it's doing. If the SERVICE is backdoored, then you have no guarantee over any other network because any/all of them can be backdoored and you would have no idea.
I do not use "whatsapp business," no idea why I would.
I do not seek to use a service and then interact with the people who happen to be on that service, I seek to interact with people and meet them on the service they're using. The fediverse is an exception, because I believe in the principles, but the experience sucks because it's all tech with no real community (Lemmy/Kbin) and none of the people I want to follow (Mastodon).