I haven't read this comic, but here are my two cents.
The-hero-is-evil is a common trope. It's one of the oldest storytelling tricks in the book - especially the superhero book. It's a way for the creators to make the readers gasp and go "No! Surely not! How could this BE? D:", so that they'll pick up the next issue and keep reading. It's a shocking twist, it's supposed to make you upset and angry that your favourite good guy is suddenly a bad guy - oh no, what will happen to the story?
So you pick up the next issue to find out.
This is not the first time Captain America has been evil. It certainly won't be the last time either. In fact, pick any big-name superhero from the Big Two, and I can PROMISE you that they have been evil at some point. Heck, there are covers from old issues of Superman where Superman is sieg heiling like a Nazi and threatening to take over the world. It has nothing to do with respecting the integrity of the character or its creators, and everything to do with selling more comics.
In a couple of issues, I promise you it's going to turn out that Cap has been brainwashed by magic, or replaced by a shapeshifter pretending to be him, or that someone witnessing this is just stuck in a horrible alternate timeline, and it's all going to be resolved and Cap is going to be non-Hydra again.
The point that Cap's Jewish creators would be offended by this is legitimate - casting a symbol of the fight against Hitler as a Hitler-sympathiser is iffy as heck (though it should be noted that I don't know if Hydra = Nazis is true in the comics, or if Hydra is its own separate fascist ideology? The MCU is muddying the waters there) but then again, there was a LOT of weird stuff done with these characters even when those creators were still alive.
Mainstream superhero comics are a strange amalgam of pulp origins and marketing ploys mixing with attempts at big-issue storytelling that very often fails to achieve any lasting value, because just as you're settling into one idea or aspect of a character, it gets scrapped and retconned. It's why I rarely read them, and when I do, I stay on the edges of it, reading old TPBs of Doctor Strange and pretending really hard that the Strange-movie isn't a thing that exists.