I can't help but think that the main reason to launch the 3090ti is so that NV can compare it against their next gen cards when the time comes, to make the price/performance look better rather than worse.
Prophecy for next launch.
"3090ti performance at only $700, that's a saving of over $1300. The more you buy, the more you save"- leather jacket man
IMO, they launched it so on paper, it's better than the 6900XT. The AMD card, with driver optimisations, has been gaining ground on the 3090 and in some instances beating it handily now. The 3090Ti is to get that 5% more that will put it top of review charts again.