It's why he was still respected. It's why, considering the Empire military command at large thinks of Troopers as replaceable clogs - not allowed any separate identity, nothing more than parts - there were groups which treated Vader more as God-being than Commander. His presence could easily turn the tide of battle, his presence often meant surviving.

Vader's men loved him. Vader loved them in return.

"Yes. Which leads me to believe they are magic-tech combinations." Made him hungry to get his hands on that knowledge. "It's something I'm exploring on separate matters. Anything I find which will further your research I will share with you." Of course it's a quid pro quo situation in Vader's mind.