What happened

Shares of video-streaming platform Rumble (RUM -0.15%) dropped on Monday following the expiration of its lock-up period over the weekend. At the close of the session, Rumble stock was down by about 12.7%.

When Rumble went public, many of its shares were held by insiders, and therefore subject to a lock-up period during which they couldn't be sold. This is common for newly public companies. It prevents insiders and early investors from hyping up the stock to retail investors early before dumping their positions.

Rumble's lock-up included more than 140 million shares held by founder and CEO Chris Pavlovski, representing 44.6% of shares outstanding, which is an unusually high percentage. That lock-up period expired on Saturday.

Therefore, Monday was the first day of trading since the lock-up expired. Pavlovski's massive quantity of shares can now be sold, at least in theory.

So what

On Sept. 5, Rumble issued a press release reassuring investors that Pavlovksi doesn't intend to sell any of his shares. And I'm not saying that Rumble stock fell on Monday because Pavlovski is breaking his promise. On the contrary, investors have no idea what he did either way.

But that's the problem. In the past, insiders at some other companies sold their shares when their lock-up periods expired. Therefore, with Rumble stock, it's likely that investors sold Monday out of fear that Rumble insiders could sell their shares, not because those insiders necessarily are selling shares.

Now what

Rumble brands itself as a platform for free speech. But it's possible to be an ardent advocate of free speech and still approach this stock with caution. Investing isn't so simple.

With Rumble, there's reason for caution. In the second quarter, monthly active users dropped to 44 million from 48 million in the first quarter. That said, there's plenty of reason for optimism as well. The company's revenue soared year over year due to improved monetization and growth in how many hours of video were streamed by users.

For now, my suggestion would be to keep Rumble's business as your top consideration when forming an investment thesis. Other considerations should be viewed as secondary.

Also keep in mind that it's only reasonable that Pavlovski will sell at least some of his Rumble shares at some point because they make up the majority of his net worth -- many CEOs sell a few shares from time to time. There are legitimate personal and financial reasons for insiders to sell shares -- such moves don't necessarily signal problems with their businesses. Therefore, investors would be well-advised to calmly assess what's going on if Pavlovski does eventually sell some of his Rumble stake.