Why has the Catholic Church grown among the biggest group of believers? Maybe because of the signs people can see. That was the surprise that moved the Apostle Thomas to exclaim “My Lord and my God” upon seeing the Risen Christ 3 days after He died. The same thing we may say of the people who come to be convinced by the numbers of Catholic believers devotedly attending Masses on feast days.
There are also concrete signs the Lord works to persuade people to believe. Like, for example, the Eucharistic miracle in Lanciano, Italy that portrays Christ’s presence in the Eucharist, body and blood. The miracle has been evaluated by scientists. For one thing if that was one deceptive occurrence, why do Catholics still believe in the sacrament of the Eucharist? And present statistics show their number as one billion and one hundred eighty one million (1,181,000,000).
The miracles that accompany those officially certified as Saints (which is a requisite) as well as other doctrinal pronouncements, are all impartially documented and filed, which you can check yourself. That’s the assurance of Jesus at the end of St. Mark’s gospel: “And so the Lord Jesus, after he had spoken to them, was taken up into heaven: there at the right hand of God he took his place, while they, going out, preached everywhere, the Lord working with them and confirming the word by the signs that accompanied it” (Mk. 16:19-20)..