Civilization 6 players have been noticing something odd with AI civs ever since the big April balance patch, which capped off the year-long New Frontier season pass of micro-expansions and free updates. For the past few months, the AI has been going gaga over science, to the exclusion of all other concerns.
I mean, who needs wealth, public health, or even a functioning military when you can just science your way out of a problem, right? One enterprising member of the community on CivFanatics decided to go investigate, and discovered that a few lines of code had been changed in the Victories.xml file. You can also read a summary on this thread over on r/civ, which goes into more detail as to why some players feel this is a problem.
Two of the code changes are to do with favoured districts, but the ring-leader of this mad science rush is a line that essentially increases the internal value of science yields by 150%. This means that all AI civs will prioritise science generation over other concerns pretty much from the start of the game, and this bias remains in place until the end.