Well Trump was always ahead in the art of persuading voters, I think he meant Trump has caught up on the art of persuading delegates.
Not really. Most of these delegates had to declare to the media who they were supporting before the vote. Some said they would support the state winner. The Trump voters seemed to be mostly aware of what delegates to vote for due to Trump distributing the lists online, by mail and at the polls. So this was a direct election, with not much persuasion necessary. Nevertheless, these 54 elected delegates are not bound by the convention rules to vote for anyone. However, they’re probably even more likely to stay loyal to Trump on multiple ballots than most delegates, because they did declare publically before the election how they planned to vote and are answerable to the people who elected them.
Any friendly delegates Cruz has gotten in are mostly bound to their state winner on the first ballot. Only if it goes to a second ballot will Cruz be able to take advantage of their loyalties, unless their state was a Cruz-win state to begin with.