We all know that in November the Republicans are almost certainly going to gain control of the House of Representatives in November.
The Republicans will clearly subpoena the basis for the search warrant on Mar-A-Lago in a few short months. Merrick Garland is not stupid. He knows that he will be called out to defend this soon and that if he does not have a basis for defending this, he will be impeached. Garland does not want to be impeached.
You are stupid if you think Garland did this without a strong basis for it.
Merrick, himself, cannot. There are judges who have to approve the warrant, and there must be overwhelming evidence there are incriminating items in the place to be searched. It's not easy to get.
He would not have asked for a warrant if he thought tthere was not good evidence for it. Even asking and being denied would have been big.