You see, the thing is: people love to think of the Titan Army as heartless traitors who left their family behind to join Kronos's evil cause.
But that's not how it was.
The Titan Army most probably didn't join Kronos's cause, rather, they believed in Luke's.
They were a bunch of teenagers, mostly comprised of Cabin Eleven campers (it is safe to assume that majority of them were unclaimed demigods) who had been under Luke's leadership for years. And even if they were not from Cabin Eleven, Luke was a respected counselor in camp. Those teenagers had seen how unfair it was for their fellow half-bloods to be treated as extras, so when Luke said he could make a better world, they joined him.
Why wouldn't they?
Luke was the camp's golden boy, he was their leader.
And to Cabin Eleven, he was their big brother.
(Luke did not realize it but he was actually a lot like Hermes--in which he never gave up on family. Because that's why he fought right? For a better life for his family.)
The Titan Army weren't good heroes turned evil. They were children who believed they were doing something good.
Children who wholeheartedly believed they would change the world for the better.
Up until their rebellion, they were campers. Being a camper was probably the only way they knew how to live as demigods. They most probably had that set up as well.
Luke and the other older campers planned camp activities such as campfires and sing-alongs and all that to lessen the anxiety of them going to war. They knew they were at a disadvantage, so they did everything to make things more comfortable for the younger ones.
These all changed of course, when Luke became Kronos's host. The Titan of Time sitting down with children around a fire? Pft.
It was such a drastic change for everyone, to see their leader act so differently.
In the earlier days, when Kronos was asleep and Luke was awake, Luke would hang out with the younger kids. That was until his body started becoming more Kronos than Luke.
And the Titan Army learned that the hard way.
(Once, there was a Hephaestus kid, probably age 8, who asked "Luke" to play with him, showing him his new cool figurine made from scraps from the forgery. But Luke was asleep then and Kronos was in charge. Let's just say the Titan Lord did not appreciate children using their resources for their toys.
When Luke woke, he had to attend a funeral of an eight year old boy.)
They were children who believed they were bringing a brighter future for fellow half-bloods. But when you're surrounded with so much hate and violence, it's hard not to be hateful and violent.
You can't be allies with monsters without turning into one.
Maybe that's why Chris never came back to the Titan Army.
Maybe that's why some demigods chose to return to Camp Half-Blood.
Maybe that's why Luke sought Annabeth, his family, to run away with him.
The Titan Army were never heartless traitors who left their family behind to join Kronos's evil cause.
Well, they weren't always.
But somewhere along their journey, the lines blurred and they had to be what they had to be to fight for the recognition and freedom they so yearned for.
To protect the family that they love so much.
No matter the cost.
The war always wins, after all.