THIS.
I get the impression that Rob might have told Jace to give up the Future Marine bullshit and put more emphasis on the "gamer" label. Note how Jace is extremely emotional and stressed throughout the video - of course, you guys might not agree with me, but I reckon Jace might have been building up to throw his hands up and admit that he's mentally ill and not a Marine (cue lots of "Optimistic" ratings?). Instead of course he veered off and stroked his ego for a bit.
As for Rob encouraging Jace to livestream - I don't think Rob has actually watched Jace's streams. He has no idea how deep the rabbit-hole goes (this is also true for Eli - if Rob finds out, we can expect Eli home soon and Jace looking very, very stupid, but I get the impression this isn't the case).
Of course, it could well be that Jace was feeling weak after his chat with Rob and decided to fish for sympathy online, just like he did with the Hangover Vlogs. Jace's life only continued to get more hilarious and less predictable after that, and I can't help feeling this is nothing more serious than that half-assed attempt at begging for validation.