My take, for what it is worth!

Extracts::
Originally Posted by olivant
Why he testified at all or didn't invoke the 5th amendment is beyond me

Originally Posted by Turnbull
As for invoking his Fifth Amendment privilege: Suppose, after being asked if he planned the murders of the heads of the Five Families, he replied, "I decline to answer that question on the grounds that my answer might tend to incriminate me." Sure, he'd avoid perjuring himself. But, everyone would know that the reason his answer "might tend to incriminate me" was that he did plan the murders
Sure thing Turnbull It also gave Tom the ammunition to gloat, relish and even demand an apology from the senate committee!
“Sir, my client has answered every question asked by this committee with utmost sincerity [!] He has not taken the 5th amendment as it was his right to do. So in all fairness I think the statement should be heard”

The chairman was perhaps goaded and pressured into
“No, no I am going to allow Mr. Corleone to read his statement I'll put it in the record” against the advice of the senator and Questadt

Originally Posted by olivant
There was nothing for Michael to gain by admitting his controlling interest in the hotels
The committee was not able to pin anything nefarious on Michael and perhaps Michael gained that he was a legitimate business man! by admitting “Just own stock in some of the hotels there but very little Also in IBM and IT&T”

How Michael was able to “live high on the hog” on very little is for another senate hearing!