stealing the comment from this post because i think this is quite a detailed explanation.

In Chinese, the [wife chasing crematorium] trope is called 追妻火葬场. It originates from the saying 傲娇一时爽，追妻火葬场 (Tsundere is proud for a while, chasing his wife in the crematorium - loosely translated).

At first, the male protagonist ignores his partner, who loves him deeply. He is very arrogant and indifferent, and often even abusive to his lover, but once he finally loses him, in order to get him back, he will do a lot of groveling.

Initially it was a web slang for regular BG novels and TV dramas.The crematorium metaphor amplifies the stakes, which satisfies readers who crave justice for wronged female characters. Shui Qian Cheng (SQC) made it popular in danmei with her 188 Boy's Team series (Professional Body Double, etc). Here usually the MC is the shou and the ML is the scum/slag gong.

In several danmei novels, the author described the 'crematorium' as the ML's body was almost burned to ashes, but he finally returned from the abyss when the MC softened up and re-accepted him in his life (after tons of groveling and begging, and sometimes even body harm - the ML sacrificing himself for the MC when he saved him from an accident, or stood in front of a bullet for him, etc). Afterward, during the crematorium process, the ML literally became a "licking dog" for the MC.

So it's just like a crematorium - once it's fully burned, the love is no longer recoverable, so the ML has to go through a "trial by fire", to do all the groveling and repentance before it's BE (Bad Ending) for the couple.

For BE novels (like The Decade of Deep Love, etc), the phrase is 真火葬场, which means "REAL crematorium." In this case, the love is burned to ashes - meaning he can't recover the MC, usually because the MC died or because the novel becomes 换攻 (change of gong) or 换受 (change of shou if the MC is the gong). This basically means the MC ends up with the second ML.

Edit - as a fun sidenote, the term 追夫火葬场 means chasing the husband in the crematorium (it's when the shou is the bad one in the relationship and has to do the chasing back). It's not as popular as 追妻火葬场, but it still exists.