I'm not sure your characterization is all that accurate.

Originally, they thought they could build a product that worked across many languages. That necessitated a "lowest common denominator" language, which is a void that has always been strangely lacking in choice, to provide an integratabtle core. Zig had only been announced a few months earlier, so it wasn't really ready to be a contender. For all intents and purposes, C, C++, and Rust were the only options.

Once the product made it to market, it became clear that the Typescript ecosystem was the only one buying in. Upon recognizing the business failure, the "multi-language" core didn't make sense anymore. It was a flawed business model that forced them into using Rust (could have been C or C++ instead, but yeah) and once they gave up on that business model they understood that it would have been better to have been written it in Typescript in the first place — and it no doubt would have been if it weren't for the lofty pie in the sky dreams of trying to make it more than the market was willing to accept. Now they got the opportunity to actually do it.