The red X's you draw are midweek highs and are often added too when we have semi-viral content(rolling stone article etc.)... that is discernible when the spike has a significant corresponding spike in the blue line as well.

The median between the mid-week high and the week-end low is more suited place to draw your black line.

We have recently had golos pick up and busy.org. This does not account for users that have migrated or are accessing through those interfaces. This is steemit.com only data.

Regarding crawlers, where are they in the first third of the graph?

That is the beauty of a baseline beginning at Zero. The challenge with this baseline is that it will be slightly affected by migration of users to alternate front-ends and CLI, but it is better than blockchain only activity stats as they don't weed out the bots.