Such a contract - where someone promises to use their (future) presidential powers in exchange for some consideration from the other party - would be illegal and unenforceable, because someone paying the president to exercise executive powers to their benefit is literally just bribery.

In what universe does this apply to the president? If the president promises a company to do X, it’s not a contract. I’m not even sure the president is allowed to make a contract with a private entity to give them a political favor.

There is no law or precedent to prohibit someone from engaging in contracts because of holding public office. In fact there is even an ongoing movement to try to get more politicians to do exactly this so that campaign promises would be more likely to be executed. Again qualified immunity would probably make these contracts impossible to enforce against a politician, but in this case the agreement would work as a defense if for some reason Oracle et al faced legal threats or fines for continuing to work with TikTok.

You can create contract, but contracts require consideration, and I don’t see how you do consideration in a case like this without it being a bribery.

Trump => Agrees to avoid interim enforcement against companies facilitating the operation of TikTok + legally clarify matters when he gets into office.

Companies => Agree to temporarily facilitate the operation of TikTok until matters are further clarified.

I don't see anything particularly controversial here.