The Mirror Lorca is complicated villain, maybe even a Byronic hero. I think he did a lot things to test the waters and prove to himself that destiny was smiling upon him. He may believed this was the only way he could or should get home.
MIRROR LORCA: Amazing, isn't it? Different universe, and somehow the
same people, had a way to find each other. The strongest argument I
have ever seen for the existence of destiny.
MICHEAL BURNHAM: I'm not sure if I believe in destiny.
MIRROR LORCA: Is that so? Sitting in that cell all alone, facing a
life sentence of solitude, future full of misery. A little part of you
had to know that wasn't the end of your story. You were destined for
something more.
MICHEAL BURNHAM: Destiny didn't get me out of prison, Captain. You did
that.
But as Kozaky mentioned in a comments, just because he hails from the Mirror Universe, does not mean he wasn't knowledgeable in starship combat, as he proved several times during the war, but perhaps more so when Discovery jumps back to the Prime Universe 9 months later (where Lorca and Discovery have been absent) and Star Fleet is loosing and Earth has become a Klingon target!
His bigger problem was that his ethics did not always line up with Star Fleet's and because Discovery's crew is full of broken characters during a time of war, he was often not contested. (Not until Cornwall shows up, anyway).
Vaulting Ambition Transcript:
MIRROR GEORGOUI: In Lorca, you saw a father, until you grew up and it
became more.
PRIME BURNHAM: You're saying Lorca and I-
MIRROR GEORGOUI: He groomed you. He chose you. [...] He told you
that destiny brought you together.
His story is more about his love for Mirror Micheal Burnham and the destiny he believed he had with her more than anything else, which I think considering she died, that love extended to Prime Burnham, listening to her advice and allowing her privileges he often didn't with others, which in return began to change him a little bit, but enough to make him change his goals or feelings about Star Fleet.
He did seem to have some grand plan with Michael in mind and Empire's future, but he would have to be a bit delusional to really believe that Prime Burnham would actually go along with it and I think that is what your question about him gets down to.
What's Past is Prologue Transcript:
MICHEAL BURNHAM: They have no idea they're flying into a battle zone. Please, Philippa.
EMPEROR GEORGOUI: I'm not Philippa to you. But you are right about one thing. He preyed on my sentiment, my weakness for your face. It
will not happen again.
And a Speech Mirror Lorca makes...
MIRROR LORCA: Hello, Philippa. (OVER COMM): I've watched for years;
you let alien races spill over the borders, flourish in our backyard,
then have the gall to incite rebellion. The Terrans need a leader who
will preserve our way of life, our race. Try as you might, it's
clearly not you. Even Michael knew that. It was her great shame. Well,
it's indecorous of me to share pillow talk. To the rest, many of you
know me. Some of you served with me. To all, I make this offer:
renounce Georgiou. The Empire is dying in her hands. But you don't
have to Not today. Michael Burnham is not to be touched. She is
integral to our future plans, a future where we together will make the
Empire glorious again.
And Mirror Lorca admitting his feelings to Prime Michael
MIRROR LORCA: I know that's hard for you to see right now because
you're blinded by your emotions. The only thing I was blinded by was
you. I know you understand that I had to lie to you, Michael, to get
home. Just like you know that the Federation is a social experiment
doomed to failure. Childish idealism. Every species, every choice,
every opinion is not equal, no matter how much they want it to be. The
strong and the capable will always rise. Like you and me. And every
living being is safer and happier knowing their place. That's why we
have a duty to lead. Like what you did that day at the Binaries. Stay
with me. Stay here and help me bring peace to this world through
strength and order, the right way. There was no one else like the
other you. And what she and I set out to achieve was gonna be
remarkable. And then I met you. And the truth is your gifts far
surpass hers. I see you, Michael Burnham. I see your power. And I'm
offering you a future. I have since the day I brought you onto the
Discovery.
And Mirror Lorca talking to Saru and contradicting what he said he believed about order of race and species:
MIRROR LORCA: I'm glad I got a chance to say good-bye to you, and the
rest of the crew. I want you to know that my admiration for you was
and is sincere. When I look at you, I see the formidable unit of
soldiers that I sculpted. If I thought for a second that any of you
were capable of relinquishing this cult-like devotion to the
Federation, I'd enlist your skills today.
SARU: We are not interested in your sentiments.
Once Mirror Lorca gets back to the Mirror Universe, it becomes much more clear that he believed he was doing all of this for the love his Michael; believing this was his destiny, but also despite everything he did have feelings for the Discovery Crew and the experiences he had with them. It just wasn't enough to make him stop what he wanted to accomplish.
