You or I don't know how many Mega Drive would be sold without Sonic. What we do know is SEGA saw a massive spike in Hardware sales after Sonic and no Mega Drive game comes remotely close to Sonic sales. Sonic was also Huge in Europe and that was a market where SEGA was totally dominated without Tom.
Actually after Sonic 2 Sonic sales weren't that high.
Also Europe Sonic was a success because they adopted the NOA strategy of giving it away for free so that's stilll due to Tom.
3DO wasn't a flop? Everyone knew it was, early in its sales its 1st year's sales were a disaster Sega was worried that the Jaguar would take away sales given the impressive spec and price point.
You literally don't know what you're saying and are switching histories around, Sega when in talks with 3Do didn't know anything about the 3Do yet and they put out their demos later than Atari, if Sega saw the 3DO was stronger than the Jaguar and more impressive they may have changed toon with releasing a 3DO machine and likely would have delayed the Saturn. It was the early Atari spec sheets and the demo's that scared Sega in regards to the Jaguar.
When it was clear both the 3DO and Jaguar was no threat and when in April 1994 SEGA was showing off the finished Saturn, that was the time to have killed off 32X and just focus on the Saturn.
Your imagination isn't a reality, it was not "clear" either weren't a threat at that time,
For jaguar it would take until the end of the year 1994 to determine it's poor manufacturing capability and niche sales numbers.
For 3DO, it would take another year (end of 95 post NA PSX sat launch) before the 3DO started being questioned for slow sales before the fire sales and game bundles started, especially since sales jumped up after the initial price cuts in 94, especially the second half, and the earlier part of 95, and it had some top rated software titles and GEX wasn't even a thing yet. But Need for Speed was and it was a big deal along with several other games like Road Rash StreetFighterIIT Super wing commander etc and then gex would sweep the rest of the year. Mags were talking about the slew of great games out coming out, and the lower prices and the interest from devs, more stores also stocked the console, and it was doing pretty decent in Japan since the 94 launch as well sooo yeah..... Easy to trash consoles back in the day with no context or education on what happened.
Regardless, the main point here is the Jaguar, which not it was not 'clear" that's why they finished and then released the damn 32x. If it was actually "clear" they would have dropped it, or made it a ill-advertised niche item that you may see in some stores while promoting the Saturn instead.
And to call a 2-year head start irrelevant is laughable. It was a lovely gift to SEGA in the west more so with various companies having enough of Nintendo contracts for development and looking to develop on other platforms and many console gamers also looking to move to 16 bit.
Sega's sales and it's library where not in a good place int hat "two-year head start" so that's a load of nonsense. Just like NEC's 3-year head start was also irrelevant. Sega wasn't competitive anywhere until Sonic, it's best selling game was MS. freaking Pac-man along with bundled sales of Altered Beast, and that wasn't even much over 2 million consoles by 1990 and then that year was also not that high, granted tom marketing strategy did give it a boost that year which gave momentum into 1991 and Sonic.
It also wasn't until hat time you saw a mass surge of developers burned by NES moving over (who were previously slowly moving to the turbografx (in japan they still were) at the time) and then some western devs who never wanted to touch the NES, also came in droves.
You're acting like the Genesis sold some significant number and had significant software interest out the gate and that two-year start helped make it substantial, that's not actually what happened, even looking at a (complete) game release list will debunk that garbage.