Why Hulk Can Speak In Thor: Ragnarok

During the latest San Diego Comic Con, fans witnessed many exciting moments, including the reveal of Darkwing Duck, the unveiling of a Flashpoint movie from DC and trailers for both AVENGERS: INFINITY WAR and THOR: RAGNAROK.
The second Ragnarok trailer gave Marvel fans everything they wanted, including more Thor on Hulk action, the return of Loki and Hulk speaking? Yes, one of the strangest developments to come out of the RAGNAROK trailer is that the MCU's version of Hulk can now speak pretty fluently. In previous films, the most we ever heard come out of Hulk's mouth were single words or phrases, including this unforgettable line from Avengers when he beats down Loki.
But when did the Hulk learn how to speak properly? Well, that question was answered by Bruce Banner/Hulk actor Mark Ruffalo after the trailer previewed during a Saturday panel:
“Because he's been the Hulk for two years now, he has the vocabulary of a two year old. So we have a speaking Hulk. Can I say that?”
To which Ragnarok director hilariously replied with:
“Too late.”
So, if Bruce Banner has been in his Hulk form for two years now, what has he been up to since he fled Sokovia in Age of Ultron? Hulk usually spends most of his time fleeing from the army, but since Thaddeus Ross is no longer an army general and has given up his pursuit of the Green Goliath, that's highly unlikely.
While it's yet to be determined where THOR: RAGNAROK fits into the MCU timeline, we can assume that the film takes place at least two years after the events of Avengers: Age of Ultron, which happened, theoretically, in 2015. If so, then that could put the events of THOR: RAGNAROK in 2017 and speed us up to the present.
So, has the Hulk been forced to fight for the Grandmaster's amusement over the past two years? That would make sense given that the Hulk's whereabouts were unknown to everyone during Civil War, which took place a year after Age of Ultron. Even Senator Ross did not know where the Hulk was located, despite his numerous government resources.
And before anyone asks what Thor has been up to during the events of Civil War, it's pretty obvious that he was bunking with his flatmate, Darryl. Because, you know, that's definitely canon to the rest of the Marvel universe.