Three systems, three answers, one meeting
Analytics reports one figure. The CRM reports another. The ad platform claims credit for more conversions than you had leads. Everyone in the room knows the numbers disagree, and the meeting quietly becomes a negotiation instead of a decision.
The usual explanation is that the tools are configured badly. Sometimes true, but it is rarely the main cause.
The main cause is that a significant share of your visitors are never counted at all, because the script meant to count them is blocked before it loads. Browsers block it. Extensions block it. Networks block it.
You are not making decisions on partial data. You are making them on data that is biased in a direction you cannot see.
Then attribution finishes the job. The lead reaches the CRM without the campaign that produced it, so the only honest answer to what worked last quarter is that nobody knows.