That is not correct. This investigation was never limited to the concept of collusion. It was to The original intent of the investigation was to "... to ensure a full and thorough investigation of the Russian govemments efforts to interfere in the 2016 presidential election...". Note nothing about collusion in that broad charter.
The Special Counsel is authorized to conduct the investigation confirmed by then-FBI Director James B. Corney in testimony before the House Permanent Select Committee on Intelligence on March 20, 2017, including:
" (i) any links and/or coordination between the Russian government and individuals associated with the campaign of President Donald Trump; and
(ii) any matters that arose or may arise directly from the investigation; and
(iii) any other matters within the scope of 28 C.F.R. §600.4(a).(c).
If the Special Counsel believes it is necessary and appropriate, the Special Counsel is authorized to prosecute federal crimes arising from the investigation of these matters...."
"Any Links" would be to investigate all relationships between members of the Trump campaign, while "...and/or coordination" would speak to collusion. So, collusion is but an aspect of the investigation.
Meanwhile the "any other matters that arise..." aspect is a typical federal prosecution catch all..... if the Feds raid your home on a computer hacking case, but find you have kiddie porn on your computer, they are compelled to move forward on a kiddie porn investigation.
Therein is Trump's problem: he hired too many corrupt individuals, which have kept federal investigators and federal prosecutors quite busy. The fact that Trump was fine having so many corrupt people on his senior staff is quite telling. The logical conclusion to the fact that Trump is comfortable surrounding himself with corruption speaks to the notion that he is likely corrupt himself.
Meanwhile, "....Rudi Giuliani recently told a friend that he expects special counsel Robert Mueller‘s final report on the Russia investigation to be “horrific.”....
This is not going to end well for Trump. We probably will be EXPANDING the investigation to make sure we got all the cancer.