A vast vast oversimplification but an example:
Universal: "We're building a new theme park, bringing loads of investment and jobs into the area"
Government/political figures: "Fantastic, we fully support that sort of thing!"
Further down the line:
Universal: "So that theme park, we can build it but we can only do it if you can provide £xxx million for rail and road improvements and drop the VAT for the tourism industry. We'll be bringing in hundreds of jobs don't forget"
Government: "That's far too much. We can only provide £xx million for roads, we're spending rail money elsewhere and there's no budget to reduce VAT across the industry"
Universal: "Then we'll have to reconsider our investment"
I have no doubt any government will be extremely positive regarding such an investment in the UK. But as with anything, the devil is in the details. Yes, the project will bring large benefits in terms things like tax to the country's finances - but the return on that could be far slower than the money that would be lost in the short term from infrastructure spending and things like potential tax incentives.
As has already been pointed out, things like HS2 etc sounded great on paper to many, but once you get into the nitty gritty of finances the appeal has started to wear off with those who hold the purse strings. It's also got to be justified with the wider public - Someone in Alnwick wonders why all this money is being spent on a theme park when he's still waiting for the A1 to be dualed where he lives which would bring economic benefit to the area. Someone in Huddersfield wonders why all these rail improvements are being made for a theme park despite her commute to Manchester frequently being delayed or cancelled.
So while general support right now is fantastic, I don't think we should necessarily believe that support is a given once the details are revealed of the conditions Universal require in order to go ahead with a potential park. Governments have spending rules they want to stick to, and a wider public image to uphold across the whole country.
Of course, Universal could ask for nothing - but they're a business at the end of the day and I'd be surprised if they didn't require
something with all the outlay they're putting in. So I'm merely suggesting attitudes can change as more details of requirements are revealed. That could all go swimmingly in the best case, cancellation at the absolute worst or delays while discussions take place. I think it'll be the middle ground personally, and it's one of the reasons I see 2030 as being overly keen, and why I don't think it's just smooth sailing through to it opening.