We used 2 different axes because the values for each of the lines were different. For instance, in the graph comparing open tech jobs to the bar, the bar is the average technical in interviews from 1 to 4. It wouldn't have made sense to put that on the same axis as the number of open tech jobs (hundreds of thousands).
I'd go further and consolidate the chart into one line: engineers per open tech jobs. It's really hard to get much out of the red line being so close to the bottom.
Doing this would be easier to understand as a job seeker. For a given job post, I want to know if I'm competing against 10 or 50 other people on the job market.
The red axis is quite confusing, as "total engineers looking for jobs" is a much more useful point of comparison rather than "new engineers" starting from 0 at an arbitrary date.
That is, it's more important to know whether we went from 100K to 110K (and how 110K job-seekers compares to the number of job openings) than from "0" to "10".
Side note: how can the "Q4 so far" graph only go up to ~1-2000? More people than that were laid off from Twitter alone.