I'm not an expert in technology or design, but reading very well written explanations like @invesquotes seeking alfa article, facts became more clear: https://seekingalpha.com/article/4542006-why-adobe-buying-figma-for-20b

In a very simple way, the acquisition was expensive and there is some risk that it is not going to be worth in the long run. However, thinking about business, Adobe hit a home run buying its best competitor, adding capabilities to an already great portfolio of products, widening the moat and reinforcing its leader position

After all, we stand at a point where an investor has to make a decision. The most important thing for me is the investor end game. Most of them are not aware of how important it is to have a clear objective in mind. Do you want to earn money in the market or to become a shareholder and win by the success of the business at the long-term? Both choices don't look that different, but in moments like this, you have to recognize it.

If you are worried about the market in the sort term, Adobe will probably finish the year in a worse position than it was before the deal; But if you want to build wealth by being a shareholder of great companies, that will thrive in the long-term, perhaps this move by Adobe consolidated years of good results ahead. Nothing is guaranteed, but buy and holding is making choices that put chances in your favor as much as possible.