NASA had motivation, funding, and a can-do spirit. Congress has no sense of urgency, so motivation, funding, and the can-do spirit are no longer necessary for any of Congress’s pet projects. This happened to JWST even though there was an enormous amount of science expected in having JWST operate in conjunction with Hubble (view the same things at or near the same time), so time was of the essence (the clock was ticking). Now, however, we may lose the benefits of Hubble before JWST can become operational.

Congress has not only limited NASA’s funding but has deflated the can-do spirit in much of the high-value programs. The low cost projects seem to still have the motivation to get results quickly, but that could be due to the tendency of Congress to divert funds from the smaller projects to the larger ones whenever the larger ones get into trouble, so finishing on time and near budget can get the project into space before the next diversion of funds happens.

Few governments operate with a sense of urgency. This is why Toyota is not in a hurry and why ULA and Blue Origin had to delay their next rockets immediately after accepting government support for building them.
* https://behindtheblack.com/behind-the-black/points-of-information/first-ula-vulcan-launch-delayed-a-year-to-2021/

However, when commercial enterprises work on projects that they pay for, it needs to pay off sooner rather than later. SpaceX is working hard to get its Super Heavy rocket and its Starship payload, going sooner rather than later — with a sense of urgency — to the point that they seem to be preparing to begin testing almost as soon as their launch pad is complete.
https://behindtheblack.com/behind-the-black/points-of-information/spacex-about-to-install-engines-on-starship-hopper/

It is important to SpaceX that Starship-Super Heavy gets results and starts generating revenue as early as possible in order to get the return on their investment in a timely manner.

The actual cost-plus contract was awarded to Boeing in October, 1969. It specified delivery of first LRV by April 1, 1971. Boeing actually met the deadline, and the first LRV went up in July, 1971.

Kind of takes your breath away, doesn’t it? It’s amazing how many things NASA was able to accomplish so QUICKLY in 1962-1972.

Now, it’s true that the LRV was a smaller, simpler vehicle with much less in the way of performance requirements than what JAXA is talking about. LRV only had to last a few days and travel no more than 36km, nor was it pressurized. Whereas JAXA wants this new rover to have a total lunar-surface cruising range of more than 10,000 km (that would literally circumnavigate the Moon!) So some allowance has to be made here.

On the other hand, we have fifty more years of technology development. I think if you were in as big of a hurry as NASA was in 1969, you could get this thing built in a considerably shorter time than ten years. Obviously, JAXA is not in a hurry. But then neither is NASA, and they probably figure there is no point to having it done any sooner if NASA won’t even be back on the Moon before then, anyway.