All investments involve the same or greater risk. You just described precisely the risk AMD investors were required to take in financing Zen development.
AMD nearly tanked, despite having several years of performance dominance prior to Q2/Q3 2006. The only reason why AMD got away with Zen is that they already had a focused team of engineers willing to take another shot at the higher echelons of the x86 market.
And they hedged their bets by simultaneously developing an ARM core, which they later shelved when it became clear that x86 Zen would be a winner.
If in 2012-2013 an investor had taken the same amount of cash and the same debt profile as what AMD faced at the time and attempted to assemble a team of engineers to produce a competitor to Zen (and Intel), they would have failed. 100% guaranteed. That's too much intertia to overcome.
ARM and RISC-V are bigger risks
ARM? Certainly not. You can hire a much smaller team of engineers and become the next Rockchip by licensing designs directly from ARM, Ltd. Long term you wind up paying licensing fees which may cut into profits, but short term, it's much cheaper to get started that way. RISC-V does not (yet) have a good library of reference designs, but then you aren't paying any licensing fees either.
precisely because it requires customers to move away from codebases
In the consumer realm, this is a non-issue. Not many people want to use old software anymore, except maybe for games. In server maybe, but ARM server is better-represented in the software realm now. RISC-V may follow if anyone chooses to take the uarch family seriously-enough to produce performant server/workstation parts.
From a purely technological versus getting the enterprise to adopt said technologies view, I’d say Ampere, Marvell, Qualcomm/Nuvia and other are taking far bigger risks.
Only because Amazon, MS, Google, etc. have chosen to hire in-house design teams so that they don't have to buy ARM solutions from other parties. Nuvia got their payout and Ampere is still kicking.
In conclusion: it would take hundreds of millions of dollars just to acquire Zhaoxin's x86 license, and even more money to get what remains of their engineering talent. It also isn't clear that the Centaur license is transferrable, e.g. a complete transfer of the license may terminate it. Still not 100% sure how Zhaoxin has avoided that problem, but I think it's because technically they're still in a merger/cooperative agreement situation with VIA/Centaur. Regardless, all that spending plus billions more for a clean-sheet design will likely result in years of poor performance relative to the rest of the x86 market. The ARM world will also be leaving you in the dust.