not just the expansion
density measurements are also at odds, , we get a value of 0 now which means the universe is open flat , but CMB tells us it is +1 closed spherical, so it is not just expansion rates that don't match , and the answer might be it hasn't changed it just our point of perception , so it could be argued the expansion rate is fixed but relative to the expansion of the universe we( Byronic matter) now move through space/time at an accelerated rate offering us the illusion of an increase expansion rate, but that still wouldn't answer the question why the density values differ which is a bigger mystery which affects the structure of universe and not just it's expansion rate.