When LeBron went to Miami in 2010, the Heat was very different than it was when it won the NBA title in 2006. No Shaq, a somewhat diminished Wade, etc..

I think it's because Miami is a glamour city, and Cleveland is a perennial dumpster fire. Plus, in Miami LeBron colluded with two other free agents, which seems different from joining an existing star (Irving) and then recruiting another via trade (Love).

Plus the obvious that Cleveland is LeBron's home and Miami was not.