Show, don't tell. Same reason a lot of folks don't like the voiceover in Bladerunner (Harrison Ford hated it and resented having to record it). In general, text and voiceovers are considered lazy writing choices, but there can be stylistic or practical justification for them.
The original Star Wars text crawl was there to get the audience very quickly up to speed on a complicated backstory so they would understand the legendary opening shot that was about to happen - given the context (1970s audiences had no idea what was about to happen, and Lucas had a whole epic backstory no one could have known about) I think it's justified. And then that became a Star Wars tradition - basically, a meme. But it's not essential - I believe Ahsoka is the first D+ show to use one?
Here, you could make a case that we again have obscure source material, at least to the general public, so maybe you can make an argument for it on those grounds. However, I think in story terms a better opening would have been to show us the climactic battle between Ahsoka and the spy, where the audience could have got all the same information. So why not do that?
I think because using the text crawl was done for symbolic reasons, especially because it bleeds into an establishing shot that is very similar to that of the original movie (but inverted). Basically they were flagging that "this isn't like the other D+ shows, this one has the weight of the movies." It makes Ahsoka seem like a bigger deal, and also elevates its source material, the animated shows. So I get why they did it, and it wasn't the reason the opening episode irritated me so much.
The second episode is so much better than the first that I think the first had to be a "too many chefs" situation. In episode 1 the story felt really disjointed with a lot of stock scenes and a lot of exposition - basically, it seemed like they were trying to make an exciting hour that got in all the Star Wars tropes and covered a ton of backstory, at the cost of characterization. Episode 2 is much better paced and driven by character moments as much as plot exigencies. It's far better written and directed.