Loghain had understandable motivations, but he was simply too mired in his hatred of Orlais (justifiable as that is) to see the big picture. Maybe he can be forgiven for thinking at first the Darkspawn incursion wasn't a true Blight, as the Grey Wardens refuse to tell people that they know for a fact when an Archdemon is awake. But he was naive in the extreme to think that Ferelden would fall in line behind him (only likely to be true if it IS a real Blight and everyone is sufficiently scared) even if he had killed Eamon successfully. Teagan was both capable of and willing to still oppose him, as we seen in the first Bannorn scene. Yes, Redcliffe was then crippled by the Desire Demon, but that had nothing to do with Loghain and he had no way of even guessing that might happen.

His choice of allies also shows that he was in denial either about his popularity, about the threats he faced, or both. His only major ally was Arl Howe, and though we're not clear on exactly how much Loghain knew, he clearly knew about at least some to most of Howe's ugly acts. But he had no room to even stop Howe, let alone ditch him, because he's pretty much Loghain's only major ally. But more than that the fact that he knows he needs a major ally who has funding and men shows that he is deeply concerned about the Darkspawn threat, even if he thinks Ferelden can win.

I'm not even sure how good Loghain is tactically. Pulling out when Ishal is lit is the right moment in principle but hey what if those Darkspawn manage to make trouble and stop the signal fire being lit? Oh huh-doyyy guess my army's standing here until we're surrounded and overrun! Supposedly-naive Cailan was the one who wanted to make sure a couple of Grey Wardens were on the task to ensure it got done. (Cailan was a little naive, but to be fair he had little reason to fear his father-in-law and dad's best friend).

But anyway, we'll allow that Loghain does have great tactical skill. He also has poor strategic skill and zero political acumen, and it doesn't really matter how good you are at winning battles if you don't know how to use that to win the war, or indeed the peace. Eamon, conversely, knew not just what to do but how to do it, which is partly why upon his recovery he has very little trouble bringing Ferelden together even though he is never said to have any particular skill at leading men. Yes, he needs the Grey Warden's help in that, but he's the one who makes the plans, the Warden is just the best person at enacting them.

Loghain is basically undone by his own weaknesses and fears, and he's actually one of the best tragic characters I can think of in videogames as a result. He's not under the sway of a witch or an evil chancellor or any kind of Dawkspawn bulltrout or anything like that. He's just a man who grew up in a brutal war for independence, won, and is now terrified all the blood he and his companions shed will prove to be in vain. I mean, if you have Alistair fight him at the Landsmeet, what Loghain says upon losing is "So, there is some of Maric in you after all. Good." The man's love for his country (and it's a fair love, Ferelden was under Orlesian occupation for nearly the entire Blessed Age) is powerful, it's his motivation - and it's his undoing.