The 4 steps are:
1. The Vatican issues a Nihil Obstat (nothing hinders)
2. It is proved that the candidate lived "heroic virtues"
3. The first miracle
4. The second miracle
For more detail go here.
I personally believe that both John 23 and JP2 were saintly men and are in heaven and have no problem with their canonizations. However, I can see why there is a problem.
The canonization of both popes at the same time has the appearance of being about something other than the saintliness of these men. It has the appearance of being a statement, but a statement about what?
The short answer is that it is an attempt to shore up the dyke around Vatican II, a dyke that has been hemorrhaging Catholics since before it even ended.
Quite apart from the question of whether this was a Spirit-led Council is the glaring empirical fact the much expected "springtime" has not only never arrived, it has been "always winter and never Christmas", to steal a phrase from C.S. Lewis.
But now to the popes and specifically Item No. 2: heroic virtue.
In the case of John XXIII, we have a man who was pope for a very short period of time 1958 to 1963. Aside from being much loved there is little to point to in the way of "heroic virtue" (emphasis on "heroic"). In fact, though he was mostly thought of as a loving pastor, he in fact never was a pastor, spending all his days, prior to his elevation to the papacy, as a Vatican bureaucrat.
Pretty much, outside of being a nice guy, his credits amount to his calling the Second Vatican Council. I suppose that could be seen as heroic, however all his plans for the Council (the schema), as promulgated at the Roman Synod of 1960, were thrown out by the bishops on the very first day of the Council. And then he died. The end.
JP2 occupied the Chair of Peter for nearly a quarter of a century and a case for his heroic virtues, particularly in his last years, can certainly be argued. However, there are some who believe that in his waning years, he was taken advantage of and the Church began to fall into disarray, a disarray that the already old Benedict inherited, and eight years later admitted he couldn't handle. This caused some to believe that the "heroic" thing to do for JP2 would have been to step aside as Benedict did. But he didn't.
JP2 is credited with the aiding the collapse of Communism and the U.S.S.R. However, in the wake of that collapse the world quickly became a much more dangerous place and ancient tribal hatreds (particularly in the Balkans), held in check by the iron fist of Moscow, were soon let loose and morphed into genocidal campaigns and the worldwide unrest we are even seeing more of today.
I admire both men, and even named my store after John Paul II, calling it John Paul the Great Bookstore. And I am sure both are saints. However, while I do not question their canonizations, I, like many others, question the reason.