...which is why he is invoking the 5th amendment.

(Technically, he cannot even invoke the 5th amendment for any pardoned crimes because there is no longer a criminal prosecution that he can face on the charges from before the Biden autopen pardon, and thus he cannot incriminate himself on all of the lies that the diary reveals. But his legal team wants him to try to invoke it anyways because it allows him the option of not testifying for now to avoid a new crime).

As it stood as of this AM for Fauci:
If he simply admits everything in the diary as true, he loses face, but nothing more.
If the diary information is false and he contests it, he also will face no criminal charges.
But if the information in the diary is true. and he makes new lies to congress today by claiming that they are false, then he has a new crime for which he can be prosecuted.

Thus, he chose to try using the 5th amendment to spare his deteriorating reputation by not admitting his heinous acts rather than lie about it and face criminal charges or tell the truth and lose his reputation while facing no legal consequences.
It is very possible however, that because he accepted the pardon, he cannot invoke the 5th amendment, and he will be found in contempt of congress. After that plays out in court, he will be back in front of the committee if the court ruling goes against him, and he won't be able to claim the 5th amendment without facing jail time. He will be compelled to tell the truth or face jail time for lies to congress.

The diary alone is enough for reasonable people to know, but he has many devotees that need to hear it from him to believe. Your comment about this being a "false drama" demonstrates this.