Using the standard LaTeX classes (article,...), footnotes are set directly below the text if the page is in \raggedbottom instead of \flushbottom mode. The KOMA script classes change this behaviour, i.e. the footnote is placed at the very bottom of the page even if the page contains only a few lines of text.
Here is a MWE for LaTeX article:
\documentclass{article}
\usepackage[a6paper,margin=1cm,bottom=2cm]{geometry}
\raggedbottom
\title{\LaTeX{} article}
\begin{document}
\maketitle
A very short text.\footnote{A footnote.}
\pagebreak
\end{document}
and here for KOMA-Script scrartcl:
\documentclass{scrartcl}
\usepackage[a6paper,margin=1cm,bottom=2cm]{geometry}
\raggedbottom
\title{KOMA script scrartcl}
\begin{document}
\maketitle
A very short text.\footnote{A footnote.}
\pagebreak
\end{document}

Is it possible to restore the default behaviour (i.e. footnotes right below the text) without breaking the other footnote-related Koma script commands like \deffootnote, \deffootnotemark and \setfootnoterule?

\pagebreak, which isn't a good thing after all (if you don't know the difference between\newpageand\clearpage. Please inform yourself and decide, wheter\pagebreakis the way to go. – Johannes_B Mar 10 '14 at 08:44\pagebreakand\newpagein\raggedbottommode. Could you provide some details why using\pagebreakisn't a good thing? – porst17 Mar 11 '14 at 12:02