They didn't abandon Azov in the steel plant, they went to great lengths to try to extract them actually, they tried breaking out by force, they tried sneaking out, they tried rescuing them by helicopter, they tried negotiating for Russia to open a corridor to Ukrainian controlled territory, they even tried going to beg the "international community" and even the pope to intercede on their behalf. The Russians were having none of it and would only accept surrender. Azov, at least at that time, was considered one of the most politically important units for the Kiev regime.

The reason why they bombed Azovites in Russian prisons is so they couldn't tell any tales about the war crimes they committed and who ordered/gave them permission to do so. It was a necessary sacrifice and probably done by Azov themselves.

As for whether Kiev is trying to get rid of them now, yes there's an argument to be made for that based on how they keep sending them to the most difficult sections of the front, but i don't find that argument convincing for two reasons:

Firstly, i think the actual reason they keep sending them all over the place to put out fires is because they are one of the last properly trained and equipped units that Kiev has, kind of like the SS for Nazi Germany late in WW2. They have no other effective units with which to plug holes and delay the collapse of whole sections of the front.

Secondly, they hardly ever were actually sent into the most dangerous frontline fighting. Where they need meat they send some unfortunate souls who were forcefully mobilized and got a couple days of "training". Azov usually stays further away from the front and functions as a blocking detachment. And when they were sent into actually dangerous situations, like when Avdeyevka was about to fall, they simply refused to obey the orders and retreated. The fact they were never punished for that indicates that they and their political patrons still have enormous sway in the Kiev regime.

In my opinion they are still a vital unit for keeping the rest of the army from mutinying, acting as ideological enforcers and punitive squads (torturing and executing defectors, partisans, etc.), and generally being the last line of defense for the Kiev regime in case of an uprising or a regime change attempt by rival Ukrainian factions (or second to last, because the actual last line are probably western special forces).

So no, i don't think that the Nazis are being purposely eliminated, at least not by Ukraine. They are the political and military backbone of the regime.