I am having a hard time figuring out what happened.

How could I have such a decrease in online guests?

Did it stop counting bots? That seems like a lot less guests and new potential members.  Any guess?

We made two changes to bot handling in 4.3.3 (which lines up with the time you're showing).

• We consolidated and combined bot sessions instead of there being 1 session per bot (this is how 4.2 and earlier worked).
• We also added some extra entries to our bot detection.

In reality, bot guest sessions would have increased after upgrading from 4.2 and we've set those back to the usual expected levels.

Suggestion: Please show bot sessions separately in statistics.