Manafort volunteers to testify? Why?

WaPo reports that Manafort volunteered to testify to the House Intelligence Committee.  David Nunes is shouting this from the rooftops but this doesn't make Nunes look any less compromised as head of the committee. My big question is why Manafort would volunteer. Trying to control the spin?? We need an independent counsel to investigate, if there is truly nothing to hide.