Hey there boys and girls, what's happening here is called In Medias Res. The flashback started smack dab in the middle of the action before moving into the actual beginning of the flashback (and it will subsequently build up back into the action). This is a relatively common fucking thing. It's not inherently shitty writing, it's not actually badly paced at all yet.
Honestly, this makes Hashirama's peace-y bullshit so much more believable than Naruto's given the life he endured. It's like Kishi is purposefully writing all of Naruto's predecessors on the "peace" front to have much more compelling reasons for their Ninja Jesus crap than the main fucking character. Itachi, Pain, Jiraiya, now fucking Hashirama. They'd all seen actual suffering, they'd all endured a living hell. Not our plucky Ninja Jesus main character though! Really, this chapter mostly puts into perspective how goddamned petty both Naruto and Sasuke are for all their melodrama, given what their predecessors had to face.
I am a leaf on the wind. Watch how I soar.