Let me put into context just how dire the situation was for Sonic Team in the 2010's.
After the disasterous WiiU deal fell through with Lost World, the world was given a glimpse at the next era of Sonic.
It was a huge push. Comics, toys, a tv show AND games. I don't think people realise just how large of an investment Boom was.
Boom was never just a side gig for Sega, they weren't going to double their Sonic output in two seperate continuities.
The fact Sonic Boom existed AT ALL shows the desperation Sega felt to try and rebrand after the decline the franchise had felt since 2006.
You can measure the impact in the instantaneous damage Sonic 06 by comparing sales trends of hugely successful games like Sonic Rush and Secret Rings, to their post-06 sequels.
Rush Adventure didn't even crack 1 million. Which is nightmarish given how well the first game was recieved.
Sonic Boom was a hail mary to reboot the franchise, with reports stating that it may become the new "main" canon if it did well.
We heard rumors that Sonic Team would no longer be making Sonic games for consoles, which Iizuka in this recent interview more or less confirmed.
He moved to America and created Sonic Pillar - Sonic Team revamped the Hedgehog Engine, with Forces as their fanservic-y tech demo, and commissioned Headcannon/Whitehead to make Mania. That, barely, kept Sonic Team going.
Iizuka cites Mania as helping save interest in fans for the franchise, probably because it was the first game that entire decade that had any new levels to speak of that actually saw positive fan reception.
And yes, Forces was a glorified tech demo - they didn't have any actual veteran Sonic Team level designers on that game, and 3 out of the 4 years it was in development were just experimenting with the engine.
Yes, you read that right, the bulk of Forces was done in just over a year.
So, with a now-complete Hedgehog Engine 2.0 and a vision to soft reboot with an Open Zone formula with larger playspaces and expanded interactivity/combat, Sonic Frontiers became the first true game Sonic Team had invested multi-year development into.
Iizuka picks up Ian Flynn after his Metal Virus run, echoing the production of Mania to appeal to fans.
Iizuka firmly insists to his Sega bosses to give Frontiers more time. This is their last chance.
Kishimoto says the formula and Titan fights was always their ambition since before Forces.
Frontiers was essentially the game Iizuka moved countries to make. The culmination of close to a decade of effort and ambition, and drive to make sure the legacy of Sonic the Hedgehog wouldn't be that of embarassment and failure.
The Sega Investors Calling in late 2023 proudly acknowledges Sonic's return to form.
It cited the recent movie as having a positive effect, but states that Frontiers's success largely came from the fans positive reception and word of mouth, leading it to becoming the best selling game in two decades.
It says the profits would be reinvested into now-secured future of the franchise, as well as reviving other legacy IP.
So yes, 2006 almost killed Sonic, and yes Sonic Boom was the nail in the coffin, and yes SEGA was very seriously ready to shutter the series for good.
Iizuka and Sonic Frontiers saved Sonic. And arguably, the rest of Sega's legacy franchises too.
Iizuka said this was when he moved to America, which was around the time Sonic Boom happened.
There were rumors back then that given the steep decline in the franchises reputation (since 2006), Sonic Team were told they may not make Sonic games anymore.