Twitter changed their algorithm and the way they promote content.
Now if you get verified (pay Musk) - your replies get promoted and get more views and reactions. With effective removal of "old" verification system you have no way to validate whether an account is reliable or not. Everyone can look the same and virality is rewarded.
Yes but seeing as a lot of government agencies put official accounts there, even the POTUS, I assume you can understand that a lot of other people saw it as an official source of information.
Mostly journalists who can't be bothered (or don't have the wherewithal) to corroborate anything they report.