If the bad actor has centrifuge technology and access to low enriched uranium, they are already weeks away from achieving weapons grade material. If a country with Iran's enrichment capabilities had a sufficient LEU stockpile swapped for an equivalent amount of HALEU, it would shave about 7 days off the time necessary to produce a bomb's worth of weapons grade uranium.

For nations with enrichment capabilities, enrichment is not a major contributor to overall breakout time. Enrichment doesn't take much time, it's building enrichment facilities that takes a while, especially clandestinely.

Centrifuge and nuclear technology is not some latest and greatest super complicated and barely understood technology with hard to source components anymore. Old restrictions like ball bearings quality on export and such are basically meaningless today. You can buy common tooling today from China that would trounce anything people were using 60 years ago and nobody has stopped people from studying and researching nuclear technologies.

It is mostly a matter of money and international politics now. It takes a significant amount of money to build and power, and it is hard to hide the scale of building and power usage from international watchdogs. Because nothing consumes tons of energy and doesn't output tons of product to sell except for nuclear material refinement for weapons.