I don't think that is true. I've personally witnessed several major movements in France which involved literally millions of people on the streets, some of which were successful and some not. Let's look over the past 20 years:

- the anti-CPE movement (CPE was a reform for quasi-slave labor for people fresh out of studies) won after months of intense and violent struggle (think molotov cocktails) and university occupations

- the national suburbs riots of 2005 (caused by cops murdering two kids, and Sarkozy raging racist discourse) failed after weeks of intense and violent struggle ; nothing changed except some people were jailed

- in 2010-2011, the protests against retirement reform gathered over a million people every week and the government was on the verge of collapse (we no longer has gas in the petrol stations) yet the movement was never very violent, the government never ceded and so the movement lost

- in 2016, millions of people demonstrated and blockaded for months against working law reform, yet Macron (at the time "socialist" minister of economy) passed it without a vote (article 49-3 of the constitution allows the government to bypass the parliament, and it had not been used in decades) ; this was the first mass movement after the State of emergency (2015) and we can see the fascist cops were on free wheels as we started getting serious life-threatening injuries at every demo even in smaller cities

- in 2018, with the gilets jaunes, despite approval by a vast majority of the population and the protests spreading to even the tiniest countryside cities for over a year and half, the movement failed as it was teargased/grenaded/batoned to hospital (or to death, as with Zineb Redouane) and MANY people were either jailed for extensive periods of time or crippled for life

All of these protests i've noted had very clear objectives and were very massive. Some succeeded, some not. What's the difference between those cases? The only difference is the decisions by the government and the amount of blood they were willing to spill. If you want to know what kind of blood spilling i'm talking about, there's a gilets jaunes collection here: TRIGGER WARNING http://lemurjaune.fr/

On the other hand, studying the history of political repression gives us much clearer ideas on how/why social movements can succeed or fail. The fact that INTERPOL started with a "international police conference on the peril of anarchism" for example, or early collaboration between french/russian/american services to hunt down radical troublemakers. Or the Church committee investigation about FBI's COINTELPRO. Or in France, the many post-WWII scandals involving pro-nazi police prefects (like Maurice Papon who ordered to kill and deports hundreds-to-thousands of algerians in a single week of october 1961). Or the fascist militias organized by De Gaulle (Services d'Action Civique) to attack May 68 demos. Or... and the list goes on.

Modern States have spend considerable resources on counter-insurgency strategies because that's how they hold power. Whether opposition movements have a common purpose is irrelevant as long as the State has the powers and is willing to cripple or kill a significant portion of the demonstrators should their organizing start to be effective.