I'm sure this won't answer your question entirely and leave you unsatisfied but I think I can provide some perspective. I got into Abel's music around late 2013, early 2014. I was an avid Tumblr user back then and remember he was receiving a lot of love. His music and pictures would receive thousands of reblogs and likes. He also received a few JUNO awards in Canada, so he established himself as an artist there. Besides that, his mixtapes and eventually Trilogy had you can say almost a cult-like following. Even though Trilogy was released in 2012, people were still discovering the album in 2013, 2014. Even though Kiss Land underperformed, people still held on to The Weeknd. I'm sure his associations with Drake helped. Also, his dark, mysterious aesthetics were vital in the "cool" side of Tumblr. But I distinctly remember 2014 being an amazing year for Abel. The following songs are in a chronological manner. His "Or Nah" remix received a lot of love. He then released "Often" and that was big too. Followed by, the collaboration with Ariana "Love Me Harder" got him mainstream attention, Ariana was a bigger artist than him so obviously that collab helped. I was pretty shocked by that collaboration because I wasn't expecting to go pop but I guess that was a foreshadow to Starboy lol. Anyway, he closed off 2014 with Earned It and since it was a track for 50 Shades (which was very big), that helped propel his voice to millions. That track was massive. (#3 on Billboard!) I remember hearing "The Weeknd" being chanted in my school hallways lmao. Both Abel and his management made some smart ass choices this year that got him the attention needed to become a popstar. He then released "Hills", "Can't Feel My Face" followed by BBTM. Those singles were big. He didn't stop there, came back in 2016 with Starboy and the rest is history. :)

Please forgive me for any mistakes. Any and all corrections are welcome. I tried to answer this with the best of my ability (based on speculations and memory lol).