There are tons of mines which were shut down a long time ago, but could be reopened if there was much of a uranium market again.

The actual efficiency of breeding thorium is so low, it would take a HUGE scarcity to actual make any sense.

Local scarcity, not necessarily global scarcity. Especially during times of conflict. China has no uranium, so this may make sense for them.

Also, currently all transport channels for uranium are oil dependent, which is becoming a scarce resource in the relevant timeline - decades.

China has massive Uranium reserves [https://www.nucnet.org/news/chinese-state-media-announces-di...].