さてこそjust as I thought, as expected, that's why

不良(ふりょう)生徒(せいと)を宥(なだ)められて、さてこそ一流(いちりゅう)の先生(せんせい)だ。

Being able to calm down a delinquent student, just as I thought, that's why they are indeed a top-notch teacher.

見通(みとお)しの悪(わる)い交差点(こうさてん)…さてこそ事故(じこ)が起(お)きたか…。

A dangerous intersection with poor visibility... as expected, that's why an accident occurred...

少子化(しょうしか)問題(もんだい)を解決(かいけつ)して、さてこそ立派(りっぱ)な政治(せいじ)家(か)と言(い)えます。

They solved the declining birthrate issue, that's why they're a commendable politician.

両親(りょうしん)より長(なが)く生(い)きて両親(りょうしん)の死(し)に目(め)に会(あ)って、さてこそ親孝行(おやこうこう)をしたと言(い)える。

Living longer than my parents and experiencing their deaths, that's why I can say that I have fulfilled my duty as a child.

結婚(けっこん)当初(とうしょ)から喧嘩(けんか)が絶(た)えないとは思(おも)っていたが…さてこそ離婚(りこん)したか。

I had been thinking that we've been fighting non-stop since we first got married... As expected we ended up getting a divorce.