Pokemon Go question, please help! Really confused ;(

Yo guys so I saw this team mistake cough mystic gym and i decided to fk em up, as it is my Valorian duty. So i battled them all with my 678 pigeot, 546 machoke, and had 4 others ready to go vs their 3. So i kill them all, ( rip my pidgeot) but the gym doesn't get captured, wtf? Like after i kill all the enemy pokemon, it just goes back to the map and it's still blue with the same enemy pokemon I killed there. Sooo confused rn. Why didn't it turn red/get captured? Pls halp

#team valor

( fk u team instinct * cough* i mean extinct) ( mystic ur ok) ^.^