She won huge majorities in the last two elections she won as well.
Let's not forget that in 83 and 87 the Left was completely divided in on itself, and the vote badly split between Labour and the Liberal/SDP Alliance, which allowed Thatcher into office on huge majorities that our perverse electoral system sometimes throws up.
In terms of actual vote share, hers was nothing spectacular at all, John Major did better on that front in 1992 than Thatcher did in any of her elections. She won under the rules, which were and are, in my opinion, problematic. Similar things happened with Blair in 1997 and 2001 - tactical voting leading to hugely inflated majorities.
She certainly had a great amount of support but she hardly carried all before her.