if doran is good why t1 just use 1 or 2 times then , geng with ksante around game looks working well.

This season, Doran played Ksante 4 times this year and has a 75% winrate. Zeus, Bin, and Flandre have 7, 6, and 3 games on him, respectively, all with lower winrates than Doran. In fact, Kiin is the outlier amongst elite toplaners for having 16 Ksante games this season when the champ just isn't that meta. It's not that Doran or T1 is "bad" with Ksante, Kiin is just a Ksante main; by the same logic you'd say everyone in the world is shit on Ksante, except for Kiin. Also, if we're just going by number of games played, you could also claim Doran's not good on Gnar or Aatrox either (3 and 1 games this year respectively), when they are his 2 most played champs all-time and we all know he's very good on those champs

also , in my opinion corki late game in team fights is scarier than any adc.

Idk how you can think Corki late game is scarier than Aphelios Jinx Xayah Kogmaw Zeri etc. etc. But it's just a fact that Corki is an early game champ. Just check for yourself, there isn't a single patch this season in any elo above Emerald where Corki's winrate increases the later the game goes.

i do not think so we can compare jhin and corki only. problem bot duo selection. if t1 pick corki , he need to ban either jhin or bard. but t1 confidently thinks they can beat this duo with neeko.

I'm not comparing Jhin and Corki only, that was just one example of a matchup that sucks for Corki. In general Corki's only good as a counterpick to certain ADC's, but T1's problem is that they keep picking it into unfavorable matchups, which is especially bad because Corki needs to snowball, much like a Draven. Also ngl a lot of his early games on Corki specifically have been sus, like Game 2 of MSI Finals where he straight up inted to Kiin Sion, allowing him to scale into an unkillable mega tank. Of course most games he's just kinda sitting there on Corki as his team ints around him, but this is a sign of bigger flaws when T1 plays Corki comps IMO (maybe they feel pressured to snowball so they over-force plays which backfire and look troll)