I'm legitimately about to write an essay on this because I find the whole Daniel Bryan phenomenon so amazing, so bear with me.
Because he received the best babyface arc that anyone has received in this decade and most of the last - and the hilaaaarious yet baffling thing, is that most of this was apparently inadvertent. And the story doesn't even start at Summerslam 2013, I actually take you back all the way to mid 2012 when Team Hell No first formed.
Arriving to WWE and in the initial time with the company, nothing was particularly sticking for Daniel Bryan. Every few months he would change his theme song, get some different walkout attire, change his look by shaving his head or what have you. People point to the RAW after Wrestlemania as the point at which he got really over with the audience but I'd say that's the point at which people started gaining an interest in engaging with him.
The thing that actually got him over with the family audience and casuals, was his time in Hell No where people thought they were trying to bury him with a kiddish character. That was the time when the Yes/No chants got over, and that was the time Daniel Bryan started getting over because he made professional wrestling fun. People loved yanking his chain during this time, so now the association in every audience member's mind was Bryan = fun. It should be a no-brainer, epic feuds and spectacular promos are all well and good, but people go to live events TO HAVE FUN. There is always a special appreciation for characters that can provide that, and Bryan was it at the time.
Makes sense then that once he's made his singles split, everyone has very much warmed up to Daniel Bryan building up to Summerslam. He's a nice guy and your normal babyface in that sense, but most importantly in the 'what-have-you-done-for-me-lately' part of people's minds, he's the guy that made the midcard so entertaining for that period of time. It's baffling that a guy that broke his eyeball or whatever shit in the indys, should have to pay his dues again to a different audience, but he does if he wants to get over across the board, and at this point he has. Anyway, nice guy, seems to enjoy wrestling - audience is all for it, and why wouldn't you be? Who could possibly dislike the guy.
Then obviously by Summerslam 2013 it turned out HHH very much didn't like the guy. Classic pro wrestling bait and switch, and the beautiful thing was they milked Bryan's victory. They gave him confetti. They had him thank his mother and father. They had him wrestle Cena in a hard, stiff match to embody what it looked like to taste victory after a hard fought challenge. Then when HHH snatched that away from him, the audience took it very much to heart. That's when it went from the audience liking Daniel Bryan, to loving him.
After that they talked about how he's not good enough, how he's a B+ player etc etc and the crowd did identify him - not that pathetic idea that he looks like his fans(??) or whatever idiocy has been spewed - but because everyone knows what it's like to be told that you're not good enough. So they 'bury' him some more, people get upset some more, but since Bryan can't actually move forward at this point, because of The Authority having the WWEWHC on lockdown, he does the only other thing anyone in his position can do and turns to drugs.
Not actual drugs maybe, but the pro wrestling equivalent. This was the part where people thought they were trying to bury Bryan and turn him heel by joining the Wyatts since he wasn't winning the Rumble. I think of it as the moment people went from loving Bryan, to loving him A LOT. Because it evoked the exact same reactions as you get when you see someone you care about go down a bad way. When they start forming bad habits and spending time with shady people, you don't go "oh whatever, fuck you then" and they're automatically 'heel' to you now. You ask them what's wrong, try telling them that they're changing in a bad way and hope they come to their senses soon.
And when you watch that steel cage seggie you can see the audience struggling at first because they've not been taught how to convey that complexity of emotion in a wrestling arena. They want to boo, not at Bryan but at the Wyatts and at what's happening to Bryan, but they don't want anything to be misconstrued as actually booing Bryan so they mostly sit there like "...????" and hope that Bryan snaps out of it soon.
Then obviously, Bryan finally comes to his senses, turns on Bryan, and elicits the biggest reaction we'd seen in a decade.
All of that time period had so many subtle intricacies that I couldn't believe it was accidental - from the dynamic of Bryan in Team Hell No as a babyface that thought he was heel, to the crowd psychology in the Bryan/Wyatt seggie, it was all so perfectly done, and so interesting to watch unfold. Best of all it led to a top face that people were genuinely emotionally invested in. The reactions Bryan elicited from grown men and women were actually amazing to see. Too bad WWE didn't want to continue this massive success forward.
edit: did I really write that much? bloody hell.
tl;dr: Daniel Bryan's massively compelling trajectory and story arc obliged the audience to invest in him emotionally.