The lyrics of "All I Do Is Win" includes the line "Got money on my mind I can never get enough", which perfectly describes Glomgold's greedy personality.
Arguably, Glomgold's plan could have worked perfectly if he just stuck to taking Scrooge's 87 cents and maybe just messed with him a little. If it wasn't for him gluing a page in Huey's Woodchuck guidebook, they may have never caught on. Which is a prime example of one of Glomgold's biggest flaws; he makes everything way more complicated than it needs to be.
Flintheart's devil costume seems to come out of nowhere... except the first time he freezes time it can be seen in the background in a costume shop.
So after taking a day to let Scrooge rest, he, his family, and his staff just put their heads together and figured out it was Glomgold Gaslighting Scrooge with a device that can stop time. That's a pretty far leap. How'd they come to that conclusion? The episode hints at how by having Scrooge check the security cameras around the Money Bin, and even lingering on one of the cameras before moving on to the next scene. Scrooge took the day to rest, but set Gyro to reviewing the security footage in the meantime. Gyro found shots of Glomgold skulking around the Bin in his devil costume, with one of Gyro's discarded prototypes in hand. The story pretty much told itself.
Fenton is attending the funeral in his Gizmosuit. As shown eariler, Gizmoduck has his own suite of surveillance and recording features. All the better for recording an Engineered Public Confession with.
When it's announced that Scrooge has died of gold fever, Glomgold appears genuinely shocked, even though he was compleatly unfazed by every other report. That's because Gold fever was a fiction he created earlier that week, while everything else was Exactly as Planned. How could a nonexistent sickness kill someone?
It also makes his attitude during the funeral scene even more hilarious; he truely believes that Scrooge is dead from a fake disease that he made up himself!
Everyone was made aware that Scrooge had faked his deathto get Glomgold to admit fraud - all except Donald, who believed Scrooge had died for real because Louie forgot to tell him. Now taking his Hair-Trigger Temper into account, imagine what would happen if Donald hadn't left the room crying, and stayed to witness Glomgold crashing the funeral and disrespecting his beloved uncle... Or rather, try not to think about how much trouble the boys probably got into with Uncle Donald after this, especially if they told him it was all fake.
The fact that Fenton is attending as Gizmoduck suggests the Duck family was expecting for there to be a fight after Glomgold's arrival, even if they had remembered to let Donald in on the plan.
Scrooge really did seem to be losing his mind as a result of everything Glomgold was doing. If Huey didn't catch on to the fact that his guide has been altered, what could have happened as a result of Scrooge being driven mad? How far might Scrooge have gone on behalf of his missing $0.87? Might his family have had him forcibly committed?