I mean didn’t Conte do the same? To an even worst team with no chance at winning anything?
Spurs have already bought for Conte this year: Richarlison, Kulusevski, Bissouma, Perisic, Bentancur, Lenglet, Spence for about 160m total and I don't think they are done spending yet.
Conte doesn't seem the type to be worried about the "chances at winning" before joining the club, coz as long as he is backed by the owners Conte seems to have that confidence that he can create winners from scratch. Thats how he was at Juve, Chelsea & Inter, none of these teams looked like they would win when Conte joined. Spurs are a much bigger challenge for him, but only because the EPL top 2 are well established. I reckon that gap will be closed in a season or two if Spurs keep backing Conte.
In short, I can totally understand why Conte left Inter when Suning wanted to sell stars and earn money from the mercato. There was no future with this ownership. Spurs are at a lower starting point, but at least they are willing to invest to build a better future.