Crazier means more wild or unreasonable. Crazier still, it gets crazier, crazier than that.
It is the comparative of crazy and takes than. It gets crazier is the standard way of introducing a further absurdity in a story. Note that crazy has a heavy history as a word for mental illness and is generally avoided in that sense now, while surviving unremarked in these everyday uses — crazy busy, crazy about her, crazy paving.
1adjectivecrazierMore wild or unreasonable.
“The party got crazier as the night went on.”
crazier is a comparative of wildness.
crazy comes from craze + -y, akin to being "crazed up". Compare crack up (“suffered a mental breakdown; be insane”), crackpot. Compare typologically чо́кнутый.
Etymology from Wiktionary, CC BY-SA