After the Gyeyu Jeongnan, the only way for King Danjong to survive was to grit his teeth and refuse to abdicate

‌Although he lost all his power after the Gyeyu Jeongnan,
if the coup itself occurred because there was no Queen Dowager (a royal elder) to oversee it,
conversely, deposing him would not have been easy if there was no Queen Dowager to approve the coup.
Even if they did proceed, since his legitimacy was the original one, there would have been continuous public outcry from people all over the country.
The moment he abdicated, he gave Grand Prince Suyang the legitimacy to become king..
I can't help but think that if he had grit his teeth and held on without abdicating until he reached adulthood, his chances of survival would have been much higher.