A long while ago, DEATH BATTLE! also did a starter Pokémon battle royale, but this time, it is only on the Gen I starters. Lockstin considered Charizard to be in the running for victory (only behind Pikachu and Blaziken) and gave an honorable mention to Venusaur for its performance competitively, but Blastoise never made it to Top 10 in highest probability. Despite this, Blastoise won the Death Battle, and the context changes can heavily account for that. For one, Death Battle forgo'ed any and all trainer influence, so any competitive moves that made Venusaur and Charizard viable are a non-factor. Also, the decrease in participants can make Blastoise's defenses shine more, as Blastoise only had to contend with wild Venusaur and Charizard as opposed to all other starters, who may have multiple ways to work around Blastoise's shell.
Why did Rillaboom survive the fall? Its Grassy Surge ability (which reduces the damage dealt by Earthquake) can be a factor. Rillaboom is also based on a gorilla, who can climb on to things.
Pikachu turned to its trainer and nodded in understanding, which makes the set up to be a last second power of friendship move ... only for it to collapse. But this "nodding in understanding" can have another meaning — Pikachu knew that winning by plot-armor powers would be contentious, on top of Pikachu having a lot of exposure simply by being the mascot.
