Nobody is comparing them ideologically. What we see is Trump connecting with voters outside of the media crafted narrative. He has found a key issue that resonates. And he exudes optimism. Reagan was able to do that, and nobody since, until this year.
The actor was ridiculed, vilified, and not taken seriously. By his own party! What is going on today?
Given that Reagan's defining trait was his belief in limited-government, and the fact that he immediately followed a hyper-leftist and the previous title-holder for worst-ever president, I took it as an ideological reference.