I suspect it’s because with a few exceptions the 2018 and 2019 elections went even worse for them than they expected. Most of the exceptions were Republican candidates that ran poor campaigns or were poor candidates to begin with. I suspect they anticipate losing even more offices because their voter base is too stupid to remember to vote in all the positions.
the change to the ballot itself starts this year.
They swept Rat judges into Houston via straight party voting in 2018.