The entire article is about the gang and their history which goes back decades. They open the section specifically about Obama with

> Mr Trump and Mr Sessions have pointed the finger at former President Barack Obama over the spread of MS-13, alleging that his open-door immigration policies fuelled its growth. But the gang formed and flourished in the US long before Mr Obama came to power. MS-13 was identified as a significant threat in the 1990s, and a special FBI taskforce was convened against the gang in 1994.

Then strengthen that argument with a quote taken from politifacts article.

Anyway, unless you have reasons to try to distrust politifact I don't see the problem.