I agree with you to some degree. Trump has the upper hand with libertarians (aka liberal lite) and moderates, but he can’t win the general election without the support of conservatives. Cruz has the support of true conservatives, but needs more moderates to win. Unfortunately, Trump is only conservative on immigration, but the rest of his policies (abortion, gays, economics, etc) are no different than Hillary’s so I doubt Trump will appeal to conservatives in a general election. Most true conservatives will stay home rather than vote for Trump. However, moderates should be easier to win over as long as Cruz can offer them a little reality tv shock value in his speeches/debates. Luckily, conservatives are historically more reliable voters than moderates.
I think Trump offers conservatives enough to get their willing support.
Cruz offers more of course, enough for them to crawl over glass.
Cruz has to win over the majority of the moderates too though. Has to show he can do it in the primaries.
A 40% conservative who wins is worth more to conservatives than a 100% conservative who doesn’t.
So it all comes down to Cruz winning over those moderates.