1

Rw

drückt eine gewis­se Schick­sals­er­ge­ben­heit aus

man hat kei­ne Kon­trol­le über das, was einem pas­siert / über die Dnge / das Schick­sal; man soll­te etwas ein­fach [als gege­ben] hinnehmen

so ist es nun ein­mal; da kann man eben nichts machen; c’est la vie; so ist das Leben [nun mal]; so ist das nun mal im Leben.

“That’s the way the mop flops”
That is the way things happen.
Think in English 

“That’s the way the mop flops” : This is the way things hap­pen; this is typi­cal of a ran­dom pat­tern of events. (Con­tri­ved.) “Sor­ry to hear about that, but that’s the way the mop flops.”
Richard Spears, Ame­ri­can Slang

“A phi­lo­so­phic com­ment on dis­as­ter. One can also say, ‘That’s how the grape­fruit squirts’.”’ Well, the grape­fruit var. never caught on in the UK and had, I gather, only the most eph­emeral cur­ren­cy in the US. … ‘The phra­se lent its­elf to varia­ti­on, of cour­se. A fair­ly com­mon one in the 1950s—60s was “That’s the way the mop flops”; and a very local, short-lived, one in Hong Kong, 1962, after a par­ti­cu­lar­ly devas­ta­ting typho­on, code-named Wan­da! “That’s the way the typho­on wanders”.’
Eric Par­tridge, A Dic­tion­a­ry of Catch Phrases