Toby Elliott wrote the official article announcing the new change, including why and how they made the change, which I highly recommend reading, but I'll quickly summarize it and then focus on the implications to the format: What's The Change
Fallout is certainly a tech-and-artifact heavy set, however, so theres a logic there
Vivi Ornitier will also add some more punch to these decks as each Stormchasers Talent and Opt will deal damage, make Vivi bigger, and let Vivi produce more mana, continuing the onslaught
Before they could come up with a plan, Declan arrived and destroyed their Trap Cards with the effect of "D/D/D Duo-Dawn King Kali Yuga"
Matcha Splash offers reliable damage while healing your team, which can matter in longer matches
Its also the pivot around so many multicolor Commander precons