I can only half agree with you here. I really did feel that the crowd was getting behind reigns before he got injured and was out for 2 months. See the thing is I talk to a lot of casual fans (not just internet "gurus" who think they know everything) and before he got injured said fans were always talking about reigns.
After he got hurt i think he lost the crowd because he started trying to cut promos. Goldberg never cut promos, brock rarely cut promos. They were just ass kickers and it worked. Let Roman shut up and fight and he'll do fine. He has something that makes being a star easy. The guys want to be like him, and the girls love him. He has charisma....He's just not very good on the mic
As for the rumble. From the second they eliminated Bryan, the crowd boo'ed almost everything that happened. Just like they did last year when they found out bryan wasn't in the rumble. They Boo'ed the Fucking Rock!!!! They would've boo'ed almost anybody by the end of that night. So yes i wil blame roman's "failure" (i'd call it more of a bad night) on Bryan's elimination because those people weren't going to be happy with anybody winning that rumble not named daniel bryan
This "I talk to a lots of wrestling fans outside the internet" stuff always makes me laugh... What is a lot? Where do you people congregate? Do you host meetings? Seriously... I'm curious.
As for Reigns never cutting promos before he was injured - that's not entirely true. He was cutting promos on Randy Orton prior to the injury... and he was wrestling in terrible matches with Orton during that time as well. That's really when the crowd started to turn on him. This was just prior to the injury. Honestly, Reigns has been pretty awful since breaking up with The Shield. Since that time, he's been exposed for what he is... a monster face who can bring high energy in small doses. but who can't do much else in the ring.
And as for his promo ability... well that's difficult because he doesn't really have a character. There's nothing about Reigns that really defines Reigns - or differentiates him from the next "monster face." That's something that can be fixed in time, but it cant be fixed while holding the title. In fact, it was the Big Show's problem when he first won the WWE belt in 1999, and Show NEVER recovered.
Now, you mention that wrestlers have gotten over in the past w/o talking - but the two examples you gave were from 15-20 years ago... Things have changed since then. Wrestlers need to talk these days because every single show opens with a 20-minute promo. The champion can't randomly be missing from all of these. At some point, Reigns will need to actually talk. Now, it's possible that they give him a mouth piece, but Heyman is really the only one capable of doing this - and unless Reigns turns heel, then this isn't likely.
Now, as for the Rumble - Yes, they boo'ed The Rock - why? Because he was an extension of Roman Reigns. Reigns was toxic during the Rumble... not Daniel Bryan. Wanna know how I know?
Because other people got cheered during the match AFTER Bryan was eliminated. Ziggler got a huge reaction, as did Ambrose, Mizdow, Barrett and Cesaro. Now, obviously, Barrett, Mizdow and Cesaro are eons from the main event - but Ziggler and Ambrose were actually at the same level as Reigns prior to the Rumble. If the WWE had pulled the trigger on either of those guys, the audience would've been just fine. But nope - the WWE let Kane/Show dump both those wrestlers over the top rope like a sack of garbage. That's really where the crowd started spewing its venom. If they were pissed at Bryan's elimination... they were downright furious at the ridiculous booking that occurred in the final 5 minutes of the match.
Let's review:
Kane/Show throw out Ziggler with the trash. He was in the match for 2 minutes.
Kane/Show throw out Wyatt with the trash. He lasted about 40 minutes and his elimination was barely caught on camera.
Kane/Show dump out Ambrose with the trash. And now, with only 3 wrestlers believed to be in the match... the crowd knows that this whole thing was set up for Reigns to 'look strong' by eliminating the monster tandem of Kane/Show
Only... that's not what happens because Kane/Show basically eliminated each other! And then, two seconds after fighting with each other, the two big men shrug it off and attack Reigns inside the ring for no reason!
That's when The Rock came to the ring - to a huge cheer, mind you... Seriously, the pop was deafening - and cleaned house. At this point, the TV side of the audience notices that Rusev is still in the match... and they actually cheer "Let's Go Rusev!" Think about that one, though... a monster heel was hiding under the ring during the Royal Rumble. If that running away from the fight doesn't scream invincible monster, then I dont know what does!
It's only after Rusev is eliminated that the crowd let out their disgust with the decision to put over Reigns... and the match itself. The Rock was basically caught in the cross hairs.