Setting hairpin behavior at bar lines
If the note which ends a hairpin falls on a downbeat, the hairpin stops at the bar line immediately preceding. This behavior can be controlled by overriding the 'to-barline property.
\version "2.24.0"
\relative c'' {
e4\< e2.
e1\!
\override Hairpin.to-barline = ##f
e4\< e2.
e1\!
}