Is it a coincidence that economic growth has improved markedly since they took over? It's really hard to tell - it's quite a coincidence though.
The GDP growth rate seems to fluctuate significantly... It is around 1% right now, but we had negative growth for a period in early 2016 (which, last time I checked, was during the Liberal's tenure), while it was even hire in late 2011 (when the conservatives were in power).
However, I do think that overall, many of these fluctuations are out of the control of the government. Our economy can easily be influenced by outside factors (global recessions, natural disasters, etc.) I don't think the government is
powerless (they can crater the economy with something like radical protectionist trade measures), but in general many changes are out of their control.
That goes for both the Liberals (e.g. Chretien benefited by a strong global economy), and the Conservatives (who saw Canada weather the 2008 economy relatively unscathed, but who benefited by a strong resource sector).