Hexproof is irrelevant for spells and abilities that do not target. Krenko's Buzzcrusher's trigger has no targets, the lands are simply chosen and destroyed when the ability resolves, no targeting involved here. You can tell if a spell or ability is targeting by the use of the word "target". If it's there, targeted. If it's not there, untargeted. Spells and abilities can affect objects and players without targeting them.

115.10. Spells and abilities can affect objects and players they don’t target. In general, those objects and
players aren’t chosen until the spell or ability resolves. See rule 608, “Resolving Spells and
Abilities.”

115.10a Just because an object or player is being affected by a spell or ability doesn’t make that
object or player a target of that spell or ability. Unless that object or player is identified by the
word “target” in the text of that spell or ability, or the rule for that keyword ability, it’s not a
target.

115.10b In particular, the word “you” in an object’s text doesn’t indicate a target.