No, that was not obvious, nor was it even implied by the GM who fired him.
Gaudreau, Giordano, Backlund, Colborne, Brodie, Bennett, and Hamilton all had (to that point) career years in his last year here. The team played way better than their record and the only thing they didn't get for most of the year was timely saves, as Calgary had the worst SV% in the NHL due to Ramo's injury and Hiller's steep decline. Later in the year when Ortio took over the saves were there and so was team structure, but they lost some tough ones with much of their roster depth depleted after the deadline (David Jones, Jiri Hudler, Kris Russell). Even then, it was clear they were a team that played hard for Hartley, they blew McDavid and the Oilers out 5-0 in what was Edmonton's most embarassing loss, their final game in that building. Overall they closed out that season 9-6-3 which was a testament to Hartley keeping them playing for pride.
When Treliving fired him, he identified two reasons for firing Hartley - weak special teams and systems (puck possession). Of course those are important but they are not the same as players quitting on a coach. That same core legitimately quit on Glen Gulutzan last year.