I was more turned off by a couple of them (I think it was Jon and Andre... mostly Andre) being ******** on Twitter during the whole Grinch thing.
Honestly, GameExplain was one of the reasons the Grinch Hoax received so much attention.
They would cover so many leaks in videos before, most turning out to be false. So here we have the Grinch stuff that initially even people doubting it were skeptical in it being fake. But what caught people's attention was that GX, who jump at opportunities to review any major Smash news that makes noise in the fanbase, didn't say anything about the Grinch. In fact, I think it was over a week before they addressed anything with it (look how fast their Banjo Resetta video came out this week).
Then, when their analysis video finally came out, it was less than 2 minutes (from a group who do 45 minutes analysis on 20 second game trailers) and it was flimsy with a quick dismissive handwave that it was fake. Funny enough, their proof was the Banjo render in the Grinch image. Then it turned out that their proof was wrong, even having Team Fake calling them out on it. And there was no follow-up video despite them doing that before with other topics.
Then people remember that one of the GX members has insider connections. So, with how out-of-character they were acting, dismissing it with proof that was shakey at first and found to be wrong, being rude to others and adamantly avoiding the topic completely, many thought their insiders gave them orders to bury the Grinch because it WAS true and they wanted to minimize the leak's appearance. Only that made more people pay attention to it because of how uncharacteristically GX were being.
Granted, they probably knew from day 1 it was fake, but they helped fuel the fire. All they had to do was act like their usual self: analyze it early, do a 45 minute video, pretend it may be the real deal even if they knew it wasn't and leave it ambiguous and just wait and see if further details came out. But to be so delayed on looking at it and then so blunt to ignore it with bad evidence just made people think it was real.