How many people used to browse twitter without an account?
It's definitely a good question, and I can see why it may have been tempting for Elon to want to get those users to sign up, and this would be a simple solution to that, though clearly the wrong way to go about it and likely will push people further away.
Though I wonder if you really mean "browse without an account" rather than, "browse while not signed in"
Had Elon done this when he first took over, it may not have been received as poorly. The trouble is, Elon has done one thing after the other to show he's not interested in improving twitter for the users, but just to make more money for twitter. So bad decisions after bad decisions, eventually, people will have just had enough, as appears to be the case with this latest decision.
I have previously browser twitter almost ebitrley only when someone links to a post in these threads, and I read the post, and some comments and then leave. This was done without signing in, thoogh it would sometimes ask me to, I would deny as I just want to read and move on.
Elon may have even seen some stats to say something like 80 percent of viewers that aren't signed in, actually have accounts already. So he thought, why not just force them to click a few buttons, have their pc/mobile auto fill out the sign in form, and then happy days for Elon, he can now better understand and track the viewers habits with a small amount of effort from those viewers.
But people are so done with twitter. And with threads taking advantage of the situation, it's a no brainier. Move over to the site that has a trakc record of successfully running a social media site, that won't be gone any time soon, and isn't likely to make random changes for the worse 50 times in the space of 6 months.
I think something that you can easily compare it to it online stores. Sometimes I'm looking for an item and I find it only for say £20, I add to basket, go to purchase, but now the site wants me to sign up for a full account. Why can't I just guest purchase? Why do I need to make a full blown account with them. It's minimal effort sure, but I don't know if this is a one off purchase, or maybe something I'll come back to them in a few months. I want to try before I make yet another account. Instead end up just going to amazon, perhaps paying a tiny bit more, and then enjoying how easy that was. Twitter can be the same. I just want to browse first.most users don't even post, they just read and view the content/ads. When you force users to do something as simple as signing up, you're putting up a barrier, and until you've won over those users to become someone who posts, or perhaps finds a few accounts that want to follow, they have no need to sign up. And the fact those viewers are using twitter without being signed up.