The chart is confusing most comentators
It's really quite simple. The chart is a simple projection of he growth of energy production and the growth of computation. It's not intended as a prediction. Rather, it is intended to show that something must change. If the global amount of computation increases faster than does the available power, then computation will eventually consume all the energy. The data at which this happens depends on the computational efficiency. The three lines each assume a (fixed) exponential increase in computation, but at three efficiencies: "benchmark", "target", and Landauer's bound. choose any model of efficiency increase you want: your model describes a curve starting on the "benchmark" line (no efficiency increase) and eventually approaching the bound. No technology can exceed the bound: it's a law of physics. (Look it up.) So, before about 2050, either computation quits growing so fast or energy production starts growing faster.
That's still many, many orders of magnitude more computation than we are doing today, and I cannot figure out what we will be doing with it all. Note that better algorithms can make use more efficient use of the same amount of computation.