I address it because Drakon invaded his neighbors because he wanted to create an empire "under the worship of the Maker". Drakon being friends with a man who followed his religion and tolerating him isn't the same as tolerating an entire kingdom of men, women, and children who follow a different religion.
It's never contested that Drakon conquered his neighbors in religious wars - that's exactly how Orlais came to be. Drakon being nice to Andrastian convert Ameridan doesn't change that. And I bring it up because it's something to consider when you factor an entire nation of people who don't follow Drakon's religion, and Drakon's interest in expanding his empire and bringing people under the worship of the Maker (and let's not forget Amerian also makes note of Drakon's interest in bringing people to the Andrastian faith).
Indeed. In fact, this codex entry acknowledges that Orlais was going around conquering its neighbors at the time, and the in-universe anonymous University of Orlais publisher posits an alternate theory as to the true reason for the Exalted March: the conquer of Ferelden as a possible motive for Orlais trying to conquer the Dales. (Bolded parts by me) :
"The Chantry's story of the Exalted March of the Dales paints the picture of the righteous faithful arrayed against heathen savages. But I have long studied the Dales, and I find the "acceptable" version of the tale to be a poor one, laden with overt pro-Chantry and pro-human biases. Thus it is my moral imperative to propose an alternate interpretation: that the Exalted March of the Dales was nothing more than an expansionist ploy hiding behind the mask of faith.
It is easy to see on any map how large the Dales are. More importantly, they stand between Orlais and the rest of the south and would likely have represented a significant obstacle to the empire's expansion into Ferelden. Naturally, we stood to benefit from propagating the narrative of a hostile, unreasoning people attacking innocent missionaries and making blood sacrifices of good Andrastian babies. The likely truth is that the elves merely wished to maintain sovereignty over lands promised to them by Blessed Andraste herself, when the humans showed clear intent to undermine their autonomy."
I'm not saying Orlais' motivation was imperialist rather than religious, but it could have been both; intolerance toward the elven faith and autonomy, and a desire to grab their lands. A desire to put down worship of "false, heathen" elven gods in favor of their "one, true god," and a desire to bulldoze over them on their quest to expand their borders over the Dales and Frostbacks into Ferelden. The two motives work in harmony with each other, since claiming the elves are evil justifies religious invasion, and claiming the spread of faith justifies land-grabbing for border-expanding imperialists.
Personally, I think elf/human interactions reek of "whenever the elves give an inch, humans take a mile." Ameridan worshiped both the Maker and Elven Pantheon, yet the Chantry chooses to remember him as a devout Andrastian who hunted heretics. Cassandra asks of a Dalish Inquisitior, "Is there not room among your gods for one more?" yet she doesn't volunteer to add the elven pantheon to her daily prayers; and in fact shows flagrant disrespect to elven religion in the Temple of Mytha. "Why are we wasting our time with this heathen nonsense?" indeed.
Orlesian humans claimed they just wanted to send missionaries into elven territory because they wanted to give those poor elves the option to worship the REAL god if they so chose, yet the Chantry's whole founding doctrine is "Every god is wicked and false except ours, and every person not part of our religion is heathen and wicked." They also believe the Maker won't come back unless they "spread the Chant of Light to the Four Corners of the Earth." Considering the Dales stands in the way of the Chantry's eastern corner of expansion, if the Elves said "No thanks, take your Chant somewhere else," would the Chantry have really taken that lying down? They believe every faith is wicked except theirs and they have a moral obligation to spread the word to bring their god back, and those pesky elves aren't cooperating. I don't believe for one second they would have apologized and left after the elves turned them down; and I think the elves knew it too, which is why they didn't let humans bring missionaries into their borders. The elves aren't stupid. They probably saw that Orlais was going around conquering and converting its neighbors, so when Orlais (that same conqueror) sent missionaries to their doorstep, it's a small wonder they said, "Not interested!" and slammed the figurative door in their face.
P.S. Also, if the elves wanted to worship Andraste, couldn't they have formed their own religion within their borders on their own terms? The human version of her exploits has elves as barely a footnote in the whole affair, while the elves likely see themselves as integral to the whole affair. If they wanted to worship her, they could have created their own elfy version of her story with their own elfy version of worship; they didn't need humans coming in with their own human-centered religion, telling elves how they should view and worship their mortal savior.