A frequent historical claim I see being made is that the motivation behind the "Age of Discovery" was because the Ottomans blocked the trade route to the East after they conquered Constantinople.

However at the same time I have heard from others that the Iberians wanted to get around this in order to avoid the Venetian monopoly, and not because of the Ottomans.

I wanted to know how accurate these claims are and whether they are representative of historical facts?