Keep lowercase in biblatex

Family names in small caps are a default of the French localisation module. You can turn that behaviour off with

\DefineBibliographyExtras{french}{\restorecommand\mkbibnamefamily}

The \DefineBibliographyExtras{french} is necessary to make sure to overwrite the settings of the localisation module, which would otherwise take precedence over the settings in the preamble.

With the restored \mkbibnamefamily it is also possible to change the definition of \mkbibnamefamily in the preamble directly.

This seems to mean the author name is typeset in small caps. This is the default if the main language is French.

If you really don't want it, you may add these lines to your preamble:

\AtBeginDocument{\protected\def\mkbibnamefamily#1{%
\textnohyphenation{#1}}}%