Did you even look at the info at the link?
Walter Dellinger, a former U.S. assistant attorney general and solicitor general who's argued numerous cases before the Supreme Court.
Cruz started the solicitor general's job Feb. 10, 2003 and the Texas brief was filed on Feb. 17. Yet Dellinger notes that the court argument wasn't until March 26, which gave "plenty of time to prepare." "One would expect the state solicitor to argue a case of this magnitude," said Dellinger.
Someone who seems to know about Supreme Court cases thinks otherwise.
Call it 'ridiculous' if you like, but if Cruz were such a crusader for conservative principles as he considers himself to be, he would have found a way.
The timeline I referenced showed the briefs delivered in January.
Lambda Legal, who represented Lawrence.
Perhaps, your source is correct and mine in error. But that is still a telescoped schedule to deliver a SCOTUS brief from a standing start. And be aware there would be other cases awaiting attention, too, with their own priorities.
Net:net, it's unrealistic to attack Cruz for not being the front man for the Lawrence vs Texas SCOTUS case.
Finally, allow me to point out that Walter Dellinger, your source, probably has an agenda. He was a Clinton appointee. Per Wikipedia...
"He served as the acting United States Solicitor General for the 1996-1997 Term of the Supreme Court. Prior to his appointment as acting Solicitor General, Dellinger was an Assistant Attorney General and head of the Office of Legal Counsel under President Bill Clinton. He has also appeared as a commentator on This Week, the ABC News Sunday morning program hosted by George Stephanopoulos."