Mergers and acquisitions (M&A) are transactions in which one company buys, combines with, or takes a controlling stake in another. Interviewers ask "why do companies do M&A?" not to test whether you can recite a definition, but to see whether you understand that a deal is only a good idea when the combination is worth more than the sum of its parts.

The Main Reasons Companies Pursue M&A

Growing a business organically — hiring, building new products, opening new markets — takes time. M&A is often chosen because it compresses that timeline, at the cost of paying a premium up front. The recurring reasons companies acquire rather than build include:

  • Speed to capability or technology. Buying an existing product, patent, or engineering team is faster than developing it internally.
  • Scale and negotiating power. A larger combined company can negotiate better terms with suppliers, spread fixed costs over more revenue, and gain pricing power.
  • Market or geographic entry. Acquiring a local player is often faster and less risky than entering a new market from scratch.
  • Eliminating a competitor. Consolidation reduces competitive intensity and can support pricing across the combined market.
  • Synergies. Cost synergies (eliminating duplicate functions) and, less reliably, revenue synergies (cross-selling, pricing power) that neither company could capture standalone.

Strategic Buyers vs. Financial Buyers

The two main types of acquirers approach a target very differently, and understanding the distinction is a common interview follow-up.

Strategic buyers are operating companies acquiring another business to fold into their existing operations — a competitor, supplier, or adjacent player. Because they can often realize real synergies (shared infrastructure, cross-selling, purchasing power), they can justify paying a higher price than a buyer who can't capture those synergies.

Financial buyers — private equity firms, primarily — generally don't have an existing operating business to merge the target into. They can't rely on synergies the way a strategic buyer can. Instead, they evaluate the target on a standalone basis: its cash flow, how much debt it can support, and what return they can generate by improving and eventually selling it. This is why a financial buyer typically caps its bid lower than a well-matched strategic buyer for the same target — see How PE Thinks About Valuation for how that maximum-price logic is actually built.

The Test That Actually Matters: Does the Deal Create Value?

Every one of the reasons above is a story about why a deal might make sense. None of them is proof that it actually does. The premium paid over a target's standalone value has to be earned back — through synergies, net of the one-time cost of integrating the two businesses — or the deal destroys value for the acquirer's own shareholders, regardless of how good the strategic logic sounded in the boardroom.

The case What Is M&A and Why Do Companies Do It? walks through exactly that test with real numbers: computing a target's standalone value, the premium being paid, the capitalized value of expected synergies, and the resulting net value created (or destroyed) by the deal. If you want a deeper, risk-adjusted version of the synergy side of that math — including how to discount synergies for realization probability and tax them correctly — see Synergy Valuation.

Why Deals Destroy Value

The most common causes of value-destroying M&A are predictable: overpaying relative to a target's standalone worth, overestimating synergies (especially revenue synergies, which are far less reliable than cost synergies), underestimating integration costs and timeline, and letting deal momentum or competitive auction dynamics push the price past what the fundamentals support. A disciplined acquirer tests the deal against the same premium-versus-synergy framework before signing, not after.