You really want to know why Strzok, Paige and Priestap haven't been fired?

They are cooperating.

First of all, Comey threw Priestap under the bus in congressional testimony. Under oath Comney testified to congress that counterintelligence FBI investigation on the Trump team began in July 2016 and congress (Gang of 8) was not notified until March 2017. That’s an eight month period.

It is FBI practice to brief the White House (Obama), DNI (Jame Clapper) and the Gang of 8 (Nunez and Schiff) of all counterintelligence investigations quarterly. Comey only briefed the White House and DNI and avoided the Go8 for obvious reasons (they did not want Nunez to tip off Team Trump that they were under FBI surveillance).

Congresswoman Elise M. Stefanik asked Comey why Congress was not briefed on the counterintelligence investigation and Comey's response was, "Because of the sensitivity of the matter." Then she asked (paraphrasing) who made the decision to not brief congress. Comey then threw Bill Priestap under the bus and said under oath that it was Priestap's decision. Comey didn't refer to Priestap by name he only referred to him by title, Assistant Director of the FBI Counterintelligence Division.

I'm 1000% sure that pissed Priestap off.

That's why we haven't heard Priestap's name that much through this entire scandal. Priestap is cooperating with Horowitz and Huber.

Now Paige and Strzok are a bit easier. They are simply cooperating to save their jobs. The heat was put on them by releasing their text messages and they folded like cheap suits. They are spilling the beans to hold on to their careers. Whether or not that works for them we will just have to wait and see. However it's quite apparent that Paige and Strzok have made the calculation that it is better for them to cooperate.