The Mueller indictments so far point strongly toward high levels of coordination (what you mean by "collusion") between the Trump campaign and the Russians. The 7-13 indictment, for example, tells us that . . .
Indictment: justice.gov/file/1080281/d…
Mueller is obviously holding back key details. Indictments stress that more is known to the GJ than is being revealed. . .
lawfareblog.com/documents-alex… . . .
The guilty plea mentions a "presidential transition team official," who was also involved, but who Mueller didn't name. . .
lawfareblog.com/michael-flynn-…
If you want to see some legal analysis from facts given in reputable news sources (and the indictments and plea agreements) see:
The questions are not: Were crimes committed? or: Was there coordination between the Trump campaign and Russia?
The question is: Why don't the Republicans care that such crimes were committed?