The stock market moved lower on Monday, with major benchmarks indexes falling as much as 0.4% as market participants started to handicap the question of whether lawmakers on Capitol Hill would be able to come to a consensus on tax reform. Concerns that tax cuts would cause the federal deficit to skyrocket led some in Congress to consider a slower, phased-in approach, which would have less of an immediate positive effect on companies. Such a result would also raise the specter of lawmakers being unable to follow through with more comprehensive, business-friendly tax changes in the future.

Yet even against that backdrop of nervousness, some companies saw their stocks rise due to more optimistic views for their specific businesses. Mattel (NASDAQ:MAT), TransEnterix (NYSEMKT:ASXC), and Dynegy (NYSE: DYN) were among the best performers on the day. Below, we'll look more closely at these companies to tell you why their stocks did so well.

Mattel investors hope for a buyout

Mattel jumped 11%, recovering every bit of its 9% drop from Friday. The toymaker's drop last week came after it announced third-quarter results that included a 13% drop in net sales and a huge loss for the period. The bankruptcy of retailer Toys R Us was a contributing factor, but Mattel's sales declined in all of its key categories, including Barbie and American Girl. Mattel even decided to suspend its dividend.

Yet Monday's rebound  came as analysts concluded that the best solution for the business might be for the toymaker to sell itself, freeing its assets from the uncertainty about its operations. Even with that gain, Mattel has still lost more than half its value in less than a year; naturally, how it fares in the coming holiday season could be decisive in what course the company charts for itself from here.

Fisher-Price Thomas & Friends train-track twist toy set box.

Image source: Mattel.

TransEnterix gets a nice review

Shares of robotic surgical company TransEnterix experienced another day of the dramatic volatility they've shown since the FDA approval of its Senhance system. That thumbs up came two weeks ago, and caused shares to triple  from pre-announcement levels. Since then, though, TransEnterix had given up more than half of its value as investors questioned what would come next for the tiny innovator.

One answer seemed to come today, as positive comments from analyst companies accompanied rumors of a possible buyout bid, led shares to jump by almost 25%.

Given the strong competition in its niche, TransEnterix might do well to ally itself with a larger partner, but traders are working without a lot of information as they attempt to parse the company's prospects.

Dynegy makes a buy

Finally, Dynegy shares climbed 5%. The power producer said that it would combine with fellow industry major Vistra Energy (NYSE:VST) in an all-stock merger. The combined entity would have 2.7 million residential customers as well as 240,000 industrial customers. Under the deal, Dynegy shareholders will get 0.652 shares of Vistra stock for every Dynegy share they own. Although the move rewards Dynegy with a premium valuation and should help produce cost savings for the combined entity, it will still be counting on a rebound in the natural gas and renewable energy markets to power a strong rebound. Until that happens, investors might not to see immediate benefits from the deal.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.