There are ways to compare trends / changes
among time series of different magnitudes.
The transformations could be as follows:
1) Use a Logarithmic Scale .In Tableau it is a property of the Axis.
2) Calculate a Percent Difference as compare to the first Mark.
In Tableau it could be done as a Quick Table Calculation --> Percent Difference.
Compute using --> Table across (or better the [Date] pill). Relative to --> First
3) Add another discrete (blue) pill on Rows (a Dimension or Measure Names)
to draw each time series in its own Pane, then use the option on the Axis:
Independent axis ranges for each row or column.
The latter is my favourite.
One more - use a dual axis.