Honestly don‘t see why not, if done right farmers can make money growing it, some rich people make money selling and investing and the state makes money from taxes. Police have more time to deal with more important stuff (they still have to deal with a lot of bureaucracy concerning weed even though decriminalized).

The main losers are those who rely on drug dealing, which to FPÖVP is also partially the boogeyman of immigrants, if they spin it right it could make their voting base happy.

As far as I see it, the thing they maybe are afraid of is backlash from catholics and socially conservatives. If they can observe it going well for their opposition in Germany, the fear of that happening here to SPÖ/Green/NEOS could be a factor too.