See, you're not thinking like TDO management here. You're thinking logically. TDO sees attractions as revenue drains more or less. Sure, if they're a big hit they have increased merch sales and maybe bring more people to the gate and probably if done right return a higher investment on capital than the TDO brass cares to admit, but they're risky. Meet n greets, restaurants, DVC, and especially stores, now those are home runs with ROI as they are guaranteed cash streams or are cheap to build or both.
So from their perspective, it makes more sense to shut down 2 attractions first (slashed costs, see? No maintenance costs or salaries for ride operators/stuntmen), THEN build a new attraction on their footprint to spread out capex over time. Then, you build the MI coaster in the existing building after Carsland. That way they don't have to foot the bill for construction simultaneously, don't have the operating costs from an MI coaster during all this time, and most importantly, they're able to say they have something NEW to get a return guest after they've seen Cars land.
Now from our perspective, yeah build the MI coaster first as it will be cheaper to do than Cars land, could be done a heckuva lot quicker, and potentially get good numbers from the tie-in with the MI prequel. And it looks like you're doing SOMETHING to combat UNI.
But I'm guessing they don't see it that way.