Some were, and based on the timeline provided by the District Court it was clear that it would be nearly impossible for the matter to be resolved expediently. i.e.: before the next election, which the President was alleged to have abused his power to interfere in. It would rely on Congress trusting that the Supreme Court would deviate extraordinarily from its normal process and decide a matter in a very short time.

And on top of this, Congress has the power to grant subpoenas. The Supreme Court has affirmed this right since the 19th Century and it's absurd that defenders of the President keep insisting that every subpoena must be fought in court, all the way up to final appeal, in order to be valid. That is expressly not what Courts have said in the past. See: https://www.scotusblog.com/2019/07/cases-and-controversies-c...