A calendar link in a first email asks a prospect to plan around you. Most people will not, and the ones who would were already looking.
A smaller ask costs nothing to accept. Permission to send something. A yes or no to a single question. One line back. Each of those turns a cold contact into a correspondence, and the meeting comes out of the correspondence.
This is not a trick. It is the difference between asking for a decision and asking for a reaction.
How we do it
We are paid for meetings that were held. That is why the ask is small: the aim is a real conversation, not a full calendar.