I saw that a while ago. I'd love to know more about the dataset behind it as Larry asked,
FWIW: Pascal/Delphi being big did not surprise me as it was what was taught in the colleges in the 70s. Today they are teaching Python and Java so we see generations of new programmers going into the world with those skills (like my own daughter).
Larry - I think the way to explain Ada, is that it was very big for a while when DoD, DoC and some of DoE when USG bids required it. But as fast as it rose, it fell pretty fast from favor.
For me, I'm always amazed at things like Javascript and PHP, but their rise is directly mapped to people creating web sites.