The economic recovery--which is global, not just in the US--began under Obama, who started out following the same formula as Bush: "Too big to fail." Some of the stock market gains (until very recently) could be attributed to Trump's pro-business rhetoric, but overseas exchanges actually have risen more than ours.

BUT: it's hardly unusual for a sitting president to take credit for good things begun by his predecessor. Obama took the victory lap when Bin Laden was killed, but Bush did most of the heavy lifting in finding Bin Laden.