Let's look at the timeline to check your claim about blablacar vs Uber:
blablacar exists since 2004, it was first covoiturage.fr and had became the market leader in France in 2008, in 2009 the began opening services in foreign countries, in 2011 the bought main competitor which started in 1997 and are confident that their market domination allow them to pivot from free to taking a 20% commission.
january 2012, Uber launches in France.
in 2013 they change their name to blablacar so it's the same name in the 10 coutries they operate, uber grows to operate in two cities in France.
2014: uber grows to 6 cities in France, blablacar adds ukraine, russia, brazil and gets 100 millions funding to tackle world market and now transports 1 million people per month.
2015: france his 2nd biggest market for uber in Europe with over 500k users per year, blablacar buy German competitor Carpooling, Hungarian competitor AutoHop and Mexican sart-up Rides now totalling 20 millions users in 19 countries and rises 200 millions to speed up world market deployment. UberPop is forced to suspend operation due to operating illegally by evading legal obligations.
2017: uber still operates illegally without a licence and European Court confirms the UberPop suspension while also confirming that Uber is a transportation company and has to follow laws and regulations.
As we can see here, by the time Uber arrived in France, blablacar had already seized the french market for quite some time, blablacar operates lawfully while uber evades legal obligations and kept at it despite repeated warnings which is probably the reason why it got into trouble.
And this is coming from someone who strongly dislike blablacar.
Then again if US tech companies paid their taxes instead of engaging in heavy tax evasion (hello apple, facebook, amazon, google, ...), and respected local laws maybe they would not get so much flak.