Shooters who didn't commit suicide afterwards: Why?

To name three high-profile ones: Tarrant, Cruz and the Santa Fe shooter. All of them had plenty of time to end it (Cruz even escaped the crime scene undetected by blending in with the crowd) but instead allowed themselves to be taken alive.

What reasons could they have for staying alive just to rot in a prison cell?

I think they all are suicidal, but I think a part of them may want to see how the event plays out and how people will react to it. There finally getting the attention and 'power' (as they see it) that they want, and want to be there to see the people who have hurt them feeling regretful or scared. What they don't realize is that these events people cry about for a few days and then move on with their lives (unless they were in the situation, most people who know about columbine for example don't research it like we do- their sad about it but move on after awhile). There not leaving the legacy they think will be left after these horrible acts, and they will have to see that with time as they sit in jail for the rest of their lives... the whole thing is sad.

I want to say it was Kip Kinkel who planned to off himself after killing his parents but couldn't bring himself to do it. So then the next day when he went to Thurston he tried to get the cops to shoot him when he was being apprehended. They pepper sprayed him instead.

As for rotting in a jail cell, it's weird and I don't really know how to put it, but Kinkel seems to be thriving in prison from what I read in a 20 year anniversary article.

I don't know why but i always thought the ones commiting suicide just hated themselves so much that they only went on a "autodestruction mode", destroying everything around them (eric & dylan  for exemple) and the ones who didn't, wanted to see the reaction they created, the fame and were somehow proud of it ( Breivek, ...).

?

I remember listening to a podcast about mass shooters (specifically Pekka-Eric Auvinen) and one of the hosts brought up the point that if a shooter wants fame or attention then surely they wouldn't kill themselves so that they can see the impact that they have on the world. Then again, most shooters are both suicidal and homicidal and would rather kill themselves than rot away in a prison cell for the rest of their life but some are too scared to pull the trigger or just don't want to.

Some got tackled / interrupted, often when reloading or if their gun jammed (Kip Kinkel.)
Others got overwhelmed by the situation until they couldn't think straight or adhere to their suicidal plan (Andrew Wurst, Trey Sesler.)
Others, mostly psychopaths, were driven primarily by homicidal impulses than by suicidal ones (Nikolas Cruz, TJ Lane) and were willing to forfeit their death in order to continue their power fantasy.
Others were delusional about their fate after capture (Dylann Roof, who thought he would be made governor.)
Still others were incapable of functioning in society and viewed the shooting and subsequent jail as an escape from that obligation (I've seen this interpretation used for Michael Carneal.)

Alvaro Castillo planned to commit suicide but his carbine jammed in the middle of the attack and he was stopped by a bailiff and a highway patrol officer.

Junior could not commit suicide because a classmate from his classroom managed to pounce on his and take the weapon from him. However, he had several suicide attempts after his arrest.