No! Lack of funding is not a major reason alone for failure. There are other important reasons why tech startup fails
1. Lack of Market research
2. Lack of Product research
3. Unscalable or Buggy Code
All above reason accounts for failure of a startup.
If you are not doing enough research on market or customer's requirement with the problem they are facing and start building product, it's going to be traumatic response.
At modern age, with so much of option, people are very clear on their choice and easily choose brand that is widely available and not the new.
Sometimes entrepreneur have enough market research and has great IDEA too, but the product they develop is not actually focussed or solves problem precisely.
Product is hard to understand or operate.
Lastly, even if you have succeeded in wining above two points, you may still fail, if your product is not scalable or is buggy. Imagine, you have done everything great and all of a sudden, now, your product can not sustain 1000 people at a time and is crashing every now and then.
Switching code base is not easy and it could be very likely that until you plan to switch, some one else from some other place will take an advantage and enter the market with much proper scalable code.
These are my personal opinion, you may have different thoughts.